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Cushing’s disease is the result of too much steroid production in the body by the adrenal glands. The adrenal glands are small glands that sit next to the kidneys and are responsible for producing hormones such as steroids and balancing the body’s electrolytes. There are two primary causes for the body to develop Cushing’s. The first is when the brain develops a tumour in the pituitary gland. The tumour in the pituitary gland sends hormones down to the adrenal gland to tell it to produce more steroids. These excessive steroids cause many unwanted changes in the body. The second form is where the adrenal gland itself develops a tumour in it (Adrenal Gland Adenocarcinoma) and also produces an elevated amount of steroids in the body. Cushing’s is a slowly progressing disease. Its signs include: increased appetite, increased drinking and urination, reduced activity, and enlargement of the abdomen. As the disease progresses, these signs intensify, and the pet may become fat, pant heavily, and lose hair evenly over each side of the body. In some cases, hair loss may be the only apparent change. Extensive laboratory tests and radiographs or ultrasound may be needed to diagnose the condition, find its cause and plan treatment. Some animals respond to medical treatment alone, while others need both surgical and medical treatment. Unfortunately, some patients grow worse despite treatment.
DIAGNOSIS: The average life expectancy for dogs with the adrenal gland tumour form of Cushings is 36 months. The average life expectancy for dogs with pituitary dependent Cushing’s is approximately 30 months with younger dogs living longer (i.e., 4 years or more). Many dogs ultimately die or are euthanized due to complications related to Cushing's disease. The pituitary tumour may spread into other parts of the brain, pulmonary thromboembolism, septicemia and diabetes may also occur and be ultimately fatal.
TREATMENT: Control, rather than cure, is the outcome of treatment in case of the pituitary form of Cushings. A drug called mitotane is the drug of choice. Mitotane selectively destroys the adrenal gland, thus causing it to produce less steroids, which in turn stops the unwanted clinical signs of the disease. Animals using mitotane must be carefully monitored, since the drugs used in therapy may cause underproduction of adrenal hormones and a shock-like state known as an Addisonian crisis. There is an alternative to mitotane called selegiline HCl (Anipryl), it is not effective for the adrenal form of Cushing, but it can be frequently effective for the pituitary form of Cushings. In the case of the adrenal form of Cushings, the adrenal tumour can be surgically removed but this is a risky procedure and needs to be done by a highly skilled surgeon. If the surgery is successful, the patient is cured of the disease. If surgery is not performed, then treatment with a drug called mitotane can be done.
Anal sacs (also called anal glands) are two small glands just inside a pet's anus. The material secreted into these glands is thick and foul-smelling. Most animals can empty these glands voluntarily for scent marking or in self-defence, like a skunk might do. Anal Sac Adenocarcinomas are rare and account for only 2% of skin tumours in dogs and 1 % of skin tumours in cats. Predisposed breeds are the English springer spaniel, dachshund, Alaskan malamute, English cocker spaniel and the German shepherd. The cancer happens equally in males and females. A characteristic of this cancer is to create increased calcium levels in the body which will cause the dog to pant and drink excessively, vomit and go off food. Spread of the cancer into the body is common. It frequently goes to the local lymph nodes and the nearby vertebrae, causing significant pain. It will also travel to the spleen and liver. Unless early detection occurs, the cancer has already spread.
DIAGNOSIS: The tumour is rarely obvious to the pet owner in its early stages, but can easily be found by a veterinarian through rectal palpation. Once the tumour becomes large enough, it causes swelling of the rectal area and it becomes difficult for the pet to defecate. After the lump is found, diagnosis can be definitively made by biopsy. It is important to learn if the cancer has spread and this can be determined by ultrasound or computed tomography (CT).
TREATMENT: Aggressive surgical removal is required to remove the cancerous anal sac. Because spread to local lymph nodes are high, radiation therapy is frequently given after surgery to increase the pet’s chances of survival. Chemotherapy can also be given to decrease the spread of the cancer throughout the body. Pets that have evidence of cancer spread to other areas of the body have an average survival time of 6 months after diagnosis. Pets without signs of cancer spread at the time of diagnosis and removal of the anal sac have an average survival time of 15.5 months.
Hemangiopericytoma is a common tumour in dogs that generally arises on the limbs and appears as a round nodule. It is different from Hemangiosarcoma (a blood vessel tumour) in that its cancer involves cells called pericytes that are associated with blood vessels, but is not a true blood vessel cell tumour. Instead of forming a useful tissue, these pericytes form tumors because improper cell division has left them with chromosome damage.Hemangiopericytomas can appear bald, pigmented or even ulcerated. The hemangiopericytoma does not spread through the body in the way one normally thinks of cancer. It does however tend to recur at the site of its original removal. When it recurs, it tends to grow back more deeply rooted and more difficult to remove than it was in its original form. If left alone it will continue to grow inexorably over usually years until it invades a part of the body that does not have extra space to allow a tumour (usually the chest cavity is the closest such area.)
DIAGNOSIS: A biopsy of the affected mass is required to make the definitive diagnosis.
TREATMENT: If left alone, this tumour eventually becomes inoperable, disfiguring, and lethal though generally this takes years. Treatment options: · Radiation therapy the hemangiopericytoma is responsive to radiation therapy. This means that the cure rate after radiotherapy is 80-90%. Only the tumour site receives radiation in this type of therapy so the patient does not become ill though the area of radiation exposure will probably lose the ability to grow hair. Effective radiation therapy unfortunately requires 15 to 18 treatments for radiotherapy to be effective the tumour must first be surgically removed without visible remaining tumour; otherwise the tumour will be too big to respond. · Repetitive Surgery Leave tumour alone for now and attempt another surgical removal when it recurs. One option is to wait and see if the tumour regrows (it usually does). When it regrows, it can be re-removed; however, when it re-grows, it is usually more difficult to remove. Every time it is removed, it re-grows more invasively making the next surgery more difficult. If a second surgery removes the visible portions of the tumour successfully, radiation therapy can again be considered as above with similar success rate. · Surgery only Remove the tumour initially and if it recurs do no further treatment This may be a realistic option for an elderly patient as the hemangiopericytoma typically requires 6 to 12 months to grow back and longer to become disfiguring or invasive. For a younger patient, this is probably a poor option as the tumour will eventually become, as mentioned, inoperable, disfiguring, and lethal. Surgery and then amputation of the limb Allow the tumour to recur then amputate the limb. This may seem extreme but it certainly resolves the lethal aspect of the tumour in a curative manner. The hemangiopericytoma does not spread distantly in the body so amputation of the limb achieves cure and does so far less expensively than radiotherapy.
Hemangiosarcoma is a malignant tumour of the body’s blood vessels. With the exception of the skin form of hemangiosarcoma, which can often be eliminated by surgery, a diagnosis of hemangiosarcoma is bad news. This tumour is associated with serious internal bleeding and rapid internal spread. Most owners are not aware that their pet has hemangiosarcoma, because it causes almost no problems until the time that the tumour starts bleeding. Until this time the pet will behave completely normally. Fortunately, it is not without therapy options and, as long as expectations are realistic, temporary remissions are possible. There are three classical locations which account for most presentations: 1) skin and subcutaneous forms, 2) on the spleen and 3) heart-based forms · The skin form of hemangiosarcoma are the best types to have as they are the most easily removed surgically and thus have the greatest potential for complete cure. The true skin form looks like a rosy red or even black growth on the skin. This form is associated with sun exposure and thus tends to form on non-haired or sparsely haired skin, such as on the abdomen, or on areas with white fur. Dogs with short white haired fur (such as Dalmatians and pit bull terriers) are predisposed to the development of this tumour. Approximately 1/3 of cases will spread internally in the malignant way we usually associate with cancer so it is important to remove such growths promptly. It is necessary to take chest radiographs and ultrasound the abdomen and the heart after the diagnosis of skin hemangiosarcoma has been made to learn if the cancer has spread inwards. Surgery alone has been associated with a 172-day (approximately 6 months) median survival time. · The spleen form of hemangiosarcoma tends to go unnoticed as the spleen is hidden deep in the abdomen and are not visible externally. Splenic growths have the unfortunate tendency to break open and bleed profusely regardless of whether they are benign or malignant. While a splenectomy (removal of the spleen) certainly ends the prospect of this type of life-threatening sudden bleed, splenic hemangiosarcoma is still a rapidly spreading malignancy. When a splenic mass is detected by ultrasound or xray, it is not possible to tell prior to surgery if it is malignant or benign. Surgery and a biopsy are needed to determine this. By time the tumour is detected and removed, the hemangiosarcoma has already spread to other tissues, frequently the heart or liver, and chemotherapy must be used to significantly prolong the pet’s life. Survival time with surgery alone is 19 to 65 days for splenic hemangiosarcoma. With chemotherapy and surgery, a median survival time is 6 months. Although chemotherapy and splenectomy are not a cure, they do allow months are additional excellent life. Heart-Based Hemangiosarcoma: Like the splenic hemangiosarcoma, the heart-based hemangiosarcoma tends to exert its life-threatening effects by bleeding. The heart is enclosed in a sac called the pericardium. When the hemangiosarcoma bleeds, the blood fills up the pericardium until it is so full that the heart inside is under so much pressure that it has no room to fill with the blood it has to pump. Chest radiographs will show the heart looking spherical due to the blood build-up in the pericardial sac. This condition, if allowed to progress, results in an emergency circulating collapse called a "pericardial tamponade" and can only be relieved by tapping the pericardium with a needle and withdrawing the excess fluid. 63% of heart-based hemangiosarcomas have evidence of tumour spread at the time of their discovery. Survival time for surgery alone (removing the pericardium and snipping off the heart-based hemangiosarcoma) is approximately 4 months. Adding on chemotherapy after surgery can increase median survival time to 175 days. The most current protocol involves injectable Adriamycin (Doxorubicin) every 3 weeks and oral cyclophosphamide at home for 3 days out of the week.
Leukemia literally means an over-abundance of white blood cells in the bloodstream. White blood cell are important cells of our blood and are responsible our pet’s overall health. The white blood cell in the body will normally elevate in response to infection, inflammation, allergy, and even stress. However, in the case of Leukemia, we are not talking about white blood cell elevations in these moderately expected ranges. The patient with leukemia has an over-abundance of a particular white blood cell in huge magnitudes. The bloodstream is swarmed with cancerous white blood cells and the bone marrow from whence they came is consumed with making cancer cells and making very few of the other blood cells we need to survive. There are many different types of white blood cells that can create leukemia, but the most common one are from the lymphocyte white blood cell. This type is called Lymphocytic Leukemia. In dogs we are not certain what cause them to develop lymphocytic leukemia but in cats we know that it can be related to the “leukemia virus”.
DIAGNOSIS: : In most of these patients, the diagnosis of lymphocytic leukemia is clear when an impossibly high lymphocyte count is seen. (A normal lymphocyte count is generally less than 3,500 cells per microliter. In lymphocytic leukemias, lymphocyte counts over 100,000 are common.) The diagnosis of lymphocytic leukemia is usually fairly obvious but the key is to determine whether the lymphocytic leukemia is chronic or acute. Normally the term “chronic” means a process or disease has been going on for a long time and “acute” means that the process started suddenly. For lymphocytic leukemia, these terms have a different meaning: they refer to how mature the cancer cells look. Lymphocytes develop from precursor cells in the bone marrow or lymph nodes and undergo several stages of development before they are released into the bloodstream. When leukemia involves earlier stages of lymphocytes, it is said to be an acute leukemia. When cells are more developed, the patient is said to have a chronic leukemia. As a general rule, the acute leukemias act more malignantly than the chronic ones. Treatment and Prognosis: Acute Lymphocytic Leukemia (ALL) is a very bad disease. Cancer starts in the bone marrow and quickly spreads to the bloodstream, spleen and liver. The bone marrow is nearly obliterated by the cancer cells, leading to deficiencies in the other blood cells the bone marrow is supposed to be making. The most common symptoms include: listlessness, poor appetite, nausea, diarrhea, and weight loss. The average age at diagnosis is only 6.2 years with 27% of patients being under age 4 years. These patients have enlarged spleens and livers and frequently lymph node enlargement. They frequently are anemic and have low platelet numbers which may cause bleeding problems. Many will have low neutrophil (an important white blood cell that fights infections) and therefore are more likely to develop infections. Dogs with ALL are generally very sick and require aggressive chemotherapy. Often they need blood transfusions because of the severe anemia or antibiotics to make up for the neutropenia. Typical chemotherapy protocols include: prednisone, vincristine, cyclophosphamide, L-asparaginase and doxorubicin. Still, even with aggressive chemotherapy only 30% of patients achieve remission and with no therapy most patients die within a few weeks. Chronic Lymphocytic Leukemia (CLL) is often the opposite of ALL. The clinical course is long (months to years) with the average age at diagnosis being 10 to 12 years. In up to 50% of cases, there are no symptoms of any kind at the time of diagnosis and the leukemia is discovered on a routine blood evaluation. Neutropenia is a rare complication of CLL, though 80% have anemia, 70% have enlarged spleens, and 40% to 50% have liver enlargement. The course of this disease is very slow with patients living 1 to 2 years even without chemotherapy. Signs that chemotherapy are needed include lymphocyte counts greater than 60,000, anemia, low platelets, or risk for a complication called “hyperviscosity syndrome”, where they become more prone to bleeding and blindness.”
Liposarcomas are rare malignant tumours of fat cells. They tend to occur in older animals without favouring either gender. The cause of liposarcomas is unknown. They are locally invasive in the surrounding deeper tissues, and will occasionally metastasize elsewhere in the body. They can feel either soft or firm and can vary in size from 1 to 12 cm. They are frequently found on the chest or the limbs, but they can affect any area of the body, and are not necessarily the progression of a previously benign lipoma.
DIAGNOSIS: A Liposarcoma is indistinguishable from its benign cousin the lipoma. Most pets as they age develop benign fat lumps called lipomas on their bodies that cause not discomfort or problem for the pet. Liposarcomas however can cause severe mobility issues as they deeply penetrate the surrounding tissues. A biopsy and histopathology (analysis of the tumour tissues under microscope), is needed to distinguish the two tumours.
TREATMENT: Aggressive surgical management is the preferred treatment for liposarcomas. The tumour should not recur if the surgical edges are determined to be free of cancer cells by laboratory tests. Histopathology will determine the grade of the tumour. With low- or intermediate-grade liposarcomas, the risk of dissemination (spread) to other parts of the body is low, less than 20%. With high-grade liposarcomas, the risk is much greater. If it is suspected that the entire tumour was not removed by surgery then radiation therapy can be used to decrease the risk of recurrence. Chemotherapy is occasionally used on high-grade liposarcomas.
Lymphoma, also called lymphosarcoma, is a highly malignant tumour of the lymph system. It is the most common form of cancer in both humans and small animals. The lymph system is a network of lymphatic vessels and lymph nodes that exist in throughout the body. They help clean the body of unwanted substances and give protection against foreign substances. The lymph nodes serve as immune system centers where these foreign substances may be presented to the cells (lymphocytes) of the immune system. There are many different types of immune-related cells; some produce anti-bodies, some circulate and destroy the foreign materials they encounter, some regulate the activity of other cells. When lymphocytes become cancerous within a lymph node, the node swells and hardens. Malignant lymphocytes readily travel through the lymph vessels to nearby lymph nodes. Soon all the nodes are enlarged. Ultimately, the bone marrow (where most blood cells are formed) is affected, the immune system is destroyed, and severe anemia and weakness claim the victim's life.
DIAGNOSIS: Lymphoma is often diagnosed when the owner finds enlarged lymph nodes in the dog’s neck, point of the shoulder, groin and behind the knees. The veterinarian will usually take a biopsy of one or more of these lymph nodes and will often ultrasound the abdomen or take a bone marrow biopsy to confirm the diagnosis. Blood work will sometimes show an elevated Calcium level. Lymphoma is classified by stage: Stage I: - only one lymph node involved Stage II: - several lymph nodes in the same general area involved Stage III: - all peripheral lymph nodes involved Stage IV: - all peripheral lymph nodes plus the spleen, liver, and/or anterior mediastinum in the chest involved Stage V: - everything in stage IV plus bone marrow involvement Prognosis: Without treatment, most pets live 6-8 weeks after the diagnosis is made. With treatment the average survival time is 1 year. With treatment the survival time may be as little as 4 months or as long as 2 years. Unfortunately for lymphoma, there is no cure.
TREATMENT: There are variations of chemotherapy protocols used to treat lymphoma. Seventy-five percent of all patients will reach remission with treatment. Once the pet comes out of remission the treatment program can be run again, but the second remission will only last ½ of the time that the first remission lasted. More aggressive programs such as the protocols that use a combination of weekly treatments of L-Asparginase, Doxorubicin, Vincristine, Cyclophosphamide and Prednisone have the longest survival times. These programs give the best results. Dogs are frequently put on drugs to decrease nausea and vomiting for the first few days after these drugs have been given but most dogs show little discomfort and only loss of some whiskers. Shorter programs that only use one or several drugs are sometimes used, but the survival time is significantly shorter. In some cases half body radiation is used to slow the disease down. This is where the patient receives radiation over ½ of its body at a time, in an attempt to kill off the cancer cells.
In cats, mammary cancer is the third most common cancer, with the most common victim being a senior female cat around age 10 to 12 years. Dogs are lucky as only about 50% of mammary tumours are malignant for them. For cats, approximately 90% are malignant with rapid spread to adjacent glands and the nearest set of lymph nodes. Siamese cats seem to have more than their fair share of this cancer. Cat owners should regularly check for even small lumps in their pet’s mammary glands. Because veins connect both the right and left sets of glands, it is easy for tumour cells to cross from one side to the other though usually the glands on the same side as the original tumour are seeded first. At first the tumour is small and may feel like a pebble or dried pea. The tumour should be removed as soon as possible in hope of removing it completely. If left alone, mammary tumours get larger and harder and ultimately burst through the skin creating a smelly, infected ulcer. Tumours will spread from the mammary glands to local lymph nodes and then on to the chest, brain, bone, and even spleen. As the mammary cancer in cats is so deadly, prevention is the best route to go to avoid this disease. Early spaying is the single most significant protective factor. Spaying before age 6 months results in a 91% reduction in risk. Spaying before age 1 year results in an 86% reduction in risk. Spaying before age 2 years leads to an 11% reduction in risk. Having given birth to kittens has no effect on mammary cancer risk. Spaying after age 2 years does not reduce the risk of mammary cancer development at all.
DIAGNOSIS: Surgery is the most effective form of treatment. Aggressive surgery yields a disease free interval of 1 year in about 50% of cats. The tumour should always be sent off for analysis as the type and grade of tumour is important to the survival rate of the cat. The pathologist examining the biopsy tissue will grade the tumour as Grade I, Grade II, or Grade III. A grade I tumour generally has a good chance of a one year survival time depending on its size and tumour type. Grade II tumours have a 57% chance at survival after a year unless chemotherapy accompanies surgery. Grade III tumours treated with surgery alone had no survivors at one year from the time of diagnosis. Tumours removed when they are less than 0.8 inches (2cm) in diameter have a median survival time of 4.5 years. Tumours removed that are greater than 1.2 inches (3cm) in diameter have a 6-month median survival time. If lymph node involvement is already present at the time of surgery or if the tumour recurs after the first surgery, then these cats will have an average of 5.5 month disease-free interval. Feline mammary tumours are generally either carcinomas or adenocarcinomas. Papillary or tubular carcinomas tend to be the least aggressive. Ductular carcinomas seem to kill cats about four times faster. Anaplastic carcinomas are the worst kind of feline mammary cancer. Chemotherapy is used to maximize disease-free interval, after surgery is performed. The most common drugs used are Adriamycin and cyclophosphamide. The primary reason that cats lose their battle with this cancer is that it cannot be completely surgically removed and it ulcerates and becomes infected or the cancer spreads to the lungs and causes lung failure.
Most pet owners do not know that the incidence of mammary tumour development in dogs is higher than that of women, with one in four unspayed female dogs developing the disease. This is a huge incidence, yet awareness among owners of female dogs is lacking. A female puppy spayed before her first heat cycle can expect never to develop a mammary tumour of any kind. The incidence of tumour development in this group is nearly zero. If she is allowed to experience one heat cycle before spaying, the incidence rises to 7% (still quite low). If she is allowed to experience more than one heat cycle, the risk is driven up to one in four.
DIAGNOSIS: Unspayed dogs, those that have had puppies, or were spayed in adulthood, fit into the high-risk group for mammary cancer development. Regular examination of the dog’s mammary glands is important in early detection of this cancer. The normal glands should be soft and pliant, especially towards the rear legs. There should be no firm lumps. If a lump is detected, see your veterinarian at once regarding possible removal. Most tumours occur in the glands nearest the rear legs. Fortunately approximately 50% of tumours found are benign. It is usually not reliable to tell if a tumour is benign or malignant by just looking at it, so the tumour or a portion of it needs to be removed and sent for laboratory analysis. Alternatively, a needle aspirate can be performed, in which a syringe is used to withdraw some cells from the growth and the laboratory can determine whether the tumor is benign or malignant with enough accuracy to determine how aggressive the surgical approach should be. Needle aspirate may be a helpful pre-operative procedure in many cases, but it should be understood that biopsy is ultimately what is necessary to determine the extent of disease.
TREATMENT: Surgery is the primary treatment for mammary tumours. In general, approximately 50% of malignant mammary tumours will have already spread by the time of surgery. This, of course, means that the other 50% are locally confined and surgery is curative. The type of tumour is obviously important in determining the prognosis and as is whether all the cancer was removed during the surgery. If it was not completely removed, one may wish to consider a second surgery to remove more tissue. Other prognostic factors include: The size of the tumour. Tumours with diameters larger than 1.5 inches have a worse prognosis than smaller tumours. Evidence of spread to the lymphatic system (such as the presence of tumour cells in a local lymph node or visible tumour cells with in lymphatic vessels on the biopsy) carries a worse prognosis. Deeper tumours or tumour attached to deeper tissue structures carries a worse prognosis. An ulcerated tumour surface and a history of especially rapid growth also carries a worse prognosis. Radiation therapy, chemotherapy, and anti-estrogen therapy have been used for incompletely removed tumours. Sometimes it is most appropriate to monitor for recurrence with periodic chest radiographs.
Mast Cell Tumours (Mastocytomas) are one of the true chameleons of the cancer world. Their appearance can vary tremendously and a tumour can change in size and appearance tremendously over a very short period. It is common for a mast cell tumour to triple in size over night if it had been somehow traumatized that day. This occurs because a mast cell tumour is made up of a large numbers of common white blood cells called mast cells. These cells exist throughout the body and they respond to foreign invaders such as parasites. The mast cell possesses granules of especially inflammatory biochemicals meant for use against invading parasites. Unfortunately mast cells will sometimes overreact to other foreign invaders that enter the body, such as pollens or bee stings. The mast cells when stimulated by these foreign substances, will release histamine and create a “histamine” or allergic reaction, often causing intense swelling and itchiness and sometimes even an anaphylactic reaction with severe consequences. Tumours made of mast cells will also release histamine and if a small skin mast cell tumour is “bumped” accidentally, the released histamine can make it swell to many times its original size in a matter of a few hours. Mast cell tumours are especially common in dogs accounting for approximately one skin tumour in every five. The Boxer is at an especially high risk, as are related breeds: English bulldog, Boston terrier. Also at higher than average risk is the Shar pei, labrador retriever, golden retriever, schnauzer, and cocker spaniel. Most mast cell tumours arise in the skin but technically they can arise anywhere that mast cells are found. The mast cell tumour does not have a characteristic appearance though because of the tumour’s ability to cause swelling through the release of granules, it is not unusual for the owner to notice a sudden change in the size of the growth or, for that matter, that the growth is itchy or bothersome to the patient. Mast cell tumours are notoriously invasive and difficult to treat.
DIAGNOSIS: Diagnosis can often be made with a needle aspirate, which collects some cells of the tumour with a needle, and the cells are examined under the microscope. The granules have distinct staining characteristics and can be recognized easily. An actual tissue biopsy, however, is needed to grade the tumour; grading is crucial to determining prognosis. The veterinarian will also want to perform blood work, chest xrays and a needle aspiration of the local lymph nodes and of the spleen to determine if the tumour has traveled to other organs/tissues. GRADE I TUMORS: This is the best type of mast cell tumour to have as it tends not to spread beyond its place in the skin. Surgery should be curative. About half of all mast cell tumours are grade 1 tumours and can be cured with surgery alone. GRADE II TUMORS: The behaviour of this type of tumour is somewhat unpredictable. Surgical excision alone may be enough to cure the patient but recent studies have shown that radiation therapy administered to the site of the tumour can cure greater than 80% of patients as long as the tumour has not already shown distant spread. GRADE III TUMORS: This is the worst type of mast cell tumour to have; they behave very invasively and aggressively. If only surgical excision is attempted without supplementary chemotherapy, a mean survival time of 18 weeks (4-5 months) can be expected.
TREATMENT: Mast cell tumours arising from the nail bed, genital areas, muzzle, and oral cavity carry a poorer prognosis. Mast cell tumours that originate in deeper tissues such as the liver or spleen carry a particularly grave prognosis. Tumours that have been present for months or years tend to be more benign. Therapy for mast cell tumours consists of surgery, radiation therapy, and chemotherapy. What combination of the above is chosen depends on the extent of spread and malignant characteristics of the tumour. If the tumour can be cured with one or even two surgeries, this is ideal. Mast cell tumours are highly invasive and very deep and extensive margins (at least 3 cm in all directions) are needed. This can be a problem for tumours located on the neck or in the mouth. Currently three anti-cancer drugs have been particularly helpful in combating mast cell disease: prednisone (steroid), lomustine, and vinblastine. To decrease the histamine effects of mast cell tumours that frequently cause inflammation and increased stomach acid secretion, antacids and antihistamines can be used.
Osteosarcoma is a common cancer of the bone, usually affecting larger dog breeds. It is usually seen in middle aged or elderly dogs but can also occur in the young. It is highly inherited especially in certain breeds such as rottweilers and mastiffs. Osteosarcoma can develop in any bone but the limbs are the most common bones affected. Osteosarcoma begins deep within the bone and becomes progressively more painful as it grows outward and the bone is destroyed from the inside out. The lameness goes from being intermittent in the early stages to constant over a 1 to 3 month time span. Obvious swelling becomes evident as the tumour grows and normal bone is replaced by tumorous bone. The soft tissue over the affected bone will also swell and appear painful. Tumorous bone is not as strong as normal bone and can break with minor injury. This type of broken bone is called a pathologic fracture and may be the finding that confirms the diagnosis of bone tumour. Pathologic fractures will not heal and there is no point in putting on casts or attempting surgical stabilization. At this point the only way to stop the pain is through amputation.
DIAGNOSIS: Any ongoing lameness in a large breed dog should be followed up with an xray. Pain killers can be quite successful in masking the pain of an osteosarcoma. During the early stages of osteosarcoma, many people frequently believe that their dog has just “sprained” its leg. If they put their dog on pain killers without having an xray taken by a veterinarian, they can postpone the diagnosis by weeks, which unfortunately delays early detection and treatment. Radiographs of osteosarcomas usually show a very typical appearance, the affected area of bone looks “eaten away” and have a “sunburst” pattern to it. Sometimes a pathologic fracture may be seen in the damaged bone. Osteosarcomas do not cross the joint space as arthritis does. In most cases, radiography is all that is needed to make the diagnosis but sometimes there are ambiguities. If the veterinarian can not tell for certain by an xray that the dog has osteosarcoma, they may do a biopsy of the bone and send the sample to the lab for a definitive diagnosis. This can be a painful procedure as the affected bone is very sensitive.
TREATMENT: Amputation of the affected bone is recommended for any tumour involving bone. When the malignant structure has been removed, it is submitted for biopsy and the diagnosis confirmed at that time. Biopsy before amputation is felt to simply add a painful procedure to the patient and, if possible, is reserved for tissue already amputated. Treatment of osteosarcoma involves two aspects: Treating the pain caused by the bone tumour and fighting the spread of cancer. Treating the pain: Dogs are often euthanized due to the pain in the affected bone. Treating the pain successfully will allow a dog to live comfortably. The pain can be controlled by several methods. · Amputation: Amputation is the removal of the affected limb, which resolves the pain completely. Many people are hesitant to have this procedure, as losing a leg is very handicapping in a person, however, most pets function extremely well on three legs, running and playing like any other dog. · Limb Sparing: In some cases a procedure called “limb sparing” can be done in order to avoid amputation and to save the leg. The tumorous bone is removed and is replaced by a bone graft from a bone bank. The joint nearest the tumour is fused (i.e., fixed in one position and cannot be flexed or extended.) Limb sparing cannot be done if more than 50% of the bone is involved by tumour or if neighbouring muscle is involved. Limb sparing works best for tumours of the distal radius (forearm bone). · Radiotherapy: In the situation of a dog that can not undergo amputation and is not eligible for a limb spare technique, a procedure called radiotherapy can be performed. Radiation therapy does not remove the cancer, but it does significantly dull the bone pain caused by the tumour. Radiation doses can be applied to the tumour in two to three doses, sometime being given on two consecutive days. Improved limb function is usually evident within the first 3 weeks and typically lasts 4 months...) When pain returns, radiation can be re-administered for further pain relief if deemed appropriate based on the stage of the cancer at that time. · Drugs: There is not one specific drug to control the pain of osteosarcoma, but frequently combinations of narcotics, gabapentin, bisphosphonates and NSAIDs can significantly improve the dog’s quality of life. The average survival time for dogs who do not receive chemotherapy for osteosarcoma is 4 to 5 months from the time of diagnosis regardless of whether or not they have amputation. Do you want your dog's last 4 to 5 months to be painful or comfortable? Treating the Cancer: Osteosarcoma is unfortunately a fast spreading tumour. By the time the tumour is found in the limb, it is considered to have already spread. Osteosarcoma spreads to the lung in a malignant process called metastasis. Prognosis is substantially worse if the tumour spread is actually visible on chest radiographs, so if chemotherapy is being contemplated, it is important to have chest radiographs taken. The cancer can also spread to other bones in the body. Chemotherapy is used to slow down the disease within the body where it will ultimately prove fatal. Three different chemotherapies are frequently used as single agents for the treatment of osteosarcoma and are given once every 3 weeks for four to five treatments. They are carboplatin, cisplatin and doxorubicin. Sometimes a combination of carboplatin with doxorubicin may be used to treat osteosarcoma. Prognosis: With the use of chemotherapy, the median survival time of osteosarcoma is 12 months. Some dogs will live for up to two years and unfortunately others as short as 6 months. Young dogs with osteosarcoma tend to have shorter survival times and more aggressive disease than older dogs with osteosarcoma. Elevations of alkaline phosphatase, one of the enzymes screened on a basic blood panel, bode poorly for dogs with osteosarcoma. These dogs have approximately 50% of the survival times of dogs without an elevation of this enzyme. The presence of tumour in lymph nodes local to the leg being amputated is also carries a poorer prognosis. Dogs with affected lymph nodes live significantly shorter (59 days) compared to 316 days average survival time in dogs where the tumour was not evident in local lymph nodes at the time of amputation.
Soft Tissue Sarcomas (STS) are tumors of mesenchymal tissue. Mesenchymal cells are cells of the connective tissue the body which include fibroblasts, muscle cells and blood vessel lining cells). Most STS arise from the skin, subcutaneous tissue (tissue immediately below the skin), or palate. The cause of STS is not generally know except in the case of the feline sarcoma virus that is thought to be associated with feline vaccinations or after high grade doses of radiation. There are several different types of STS and these include: fibrosarcoma, neurofibrosarcoma, synovial cell carcinoma and hemangiopericytoma. They may arise from any anatomic site in the body. They tend to be very aggressive locally, in that they like to send out microscopic tumour cells deep into the surrounding tissue and complete surgical removal is extremely difficult. These tumours infrequently metastasize (spread) to far away parts of the body. They respond poorly to chemotherapy and radiation therapy.
DIAGNOSIS: Fine needle aspirates can help to rule out other common cancers such as lipoma, mast cell tumor, or abscess. But for a definitive diagnosis, a carefully made small biopsy of the tumour is essential. If incomplete surgical excision is made of a STS, the tumour will often come back extremely aggressively and be almost impossible to remove with a second surgery. This is why a small biopsy to first determine what the tumour is, is essential, prior to any attempt to remove it. Xrays should be taken to see if the STS may have metastasized to the lungs. Prognosis: Prognosis is completely dependent on the surgeon’s capability to remove the entire tumour at the time of the first surgery. If he/she is successful, then the animal will be free of the disease. If the surgeon is not successful, the tumour is unlikely to ever be completely removed and eventually the tumour will reach a size that will seriously compromise the pet’s life and will result in euthanasia.
TREATMENT: If the biopsy indicates that the tumour is an STS, detailed discussion needs to occur between the client and the veterinarian to determine if the veterinarian believes that they will be successful with surgical removal of this tumour. All too commonly incomplete surgical removal of the tumour occurs and the STS rapidly regrows. Removal of these tumours is best done in the hands of an extremely skilled surgeon, so that surgical removal is complete the first time and no angry cancer cells are left behind. Frequently, STS are referred to a board certified surgeon for surgical removal, in an attempt to get the best possible outcome. Wide 2-3 cm margins are required around the entire tumour to get all microscopic cancer cells. Radiation therapy can be used in addition to surgery to kill off any cancer cells that may remain at the margin of the surgery site. Chemotherapy seems to be poorly effective, but has been used in addition to surgery in some high grade STS cases.
The squamous cell carcinoma is tumour of the epithelial cells (eg. skin) and is often one of the most heart-breaking tumours. The tumour is rapidly invasive locally but does not spread in the way we usually think of a cancer spreading until late in its course. This would seem to be a positive aspect lending itself to potential surgical removal and cure, but unfortunately that’s usually not the case. The tumour tends to arise in locations where surgery is challenging or where the tumour isn’t detectable until surgery is no longer possible. It can occur in the mouth, on the nose, the ears, toes and thorax. White haired cats are 13 more times likely to develop it than cats with coloured coats. Common dog breeds to develop this cancer are the Scottish terrier, Pekingese, boxer, poodle, Norwegian elkhound and the daschund.
DIAGNOSIS: Because the appearance of a SCC can vary, the diagnosis must be made based on a biopsy. Treatment and Prognosis: If detected early, with aggressive surgery, in some cases the cancer can be completely removed and the patient is cured. This is common in SCC of the ear pinna when the ear is amputated. However in the case of a SCC penetrating into deeper tissues, such as the nose or mouth, radiation therapy may increase survival time. At this time, systemic chemotherapy does not appear to be effective for long term control of SCC, but chemotherapy implants placed directly into the cancer site are proving to be beneficial.