Cancers Commonly Treated

Comprehensive

cancer care can involve staging of the cancer, removal of the primary tumor, and chemotherapy treatments, as well as addressing pain control, nutrition, and overall health and wellness concerns.

Lymphoma

A name given to a group of cancers arising from the malignant transformation of lymphocytes (a type of white blood cell).

Lymphoma is a name given to a complex of abnormally proliferating lymphocytes (a type of white blood cell).  It can affect any species, age, or body region. The most common presenting sign we see in dogs is generalized enlarged lymph nodes. In cats, vomiting, diarrhea, and weight loss are more common.

Aspiration or biopsy of the affected area, followed by cytology or histopathology, are the most common techniques used to diagnose lymphoma. Sometimes we send the samples out for “typing” into either B-cell or T-cell lines. Knowing which line it is doesn’t change the treatment, but it changes the prognosis. In general, B-cell is more responsive to chemotherapy than T-cell.

Low grade (lymphoblastic) lymphoma is treated with a combination therapy. We use either the 19-week or 25-week Madison-Wisconsin protocol. Either way, the patient receives four cycles of intravenous treatments of vincristine-cyclophosphamide-vincristine-doxorubicin. The longer protocol gives them some weeks with no treatments, whereas the shorter keeps going with weekly treatments throughout. Patients that come out of remission after this course are treated with any of several rescue protocols.

Two other options are to either treat with doxorubicin alone (every three weeks for five treatments) or prednisone alone (for life).

Cats with high grade (lymphocytic) lymphoma of the intestinal tract are treated with oral chlorambucil and prednisolone at home (for life).

These numbers are averaged across several published case reports.

CR = complete remission = the percentage of treated patients which have no detectable cancer cells after treatment (this does not mean that the patient is cured).

Median Survival = the time at which half of the treated patients are expected to still be alive.

TreatmentCR rateMedian Survival
Dog: Madison-Wisconsin94%13.2 mo
Dog: doxorubicin alone59%-79%7.3-9 mo
Dog: prednisone alone50%1 mo
Cat: Madison-Wisconsin50%-70%12 mo
Cat: doxorubicin alone< 50%< 12 mo
Cat: chlorambucil/pred69%11+ mo

Osteosarcoma

Osteosarcoma is an aggressive cancer arising from bone. It is possible to have it develop in soft tissues, but this is rare.

Osteosarcoma is a malignant cancer originating form bone cells. It is possible to have it develop in soft tissues, but this is rare.  The classic case of osteosarcoma is a large-breed dog with a firm, painful swelling over the ends of long bones – away from the elbow and toward the knee. X-rays reveal bone with a “moth-eaten” appearance and a “sunburst” pattern.  Bone tumors are very painful, and limping is the most common sign.

An initial diagnosis typically comes from taking an x-ray of the limb the patient is limping on and observing changes in the bone structure. Definitive diagnosis comes from taking a biopsy of the affected bone and having it examined in a laboratory.

The longest survival rates for pets with osteosarcoma are achieved with a combination of leg amputation followed by chemotherapy. Limb-sparing surgery (removal of the affected bone and replacement with cadaver bone) is available instead of amputation, but it is only done in specialty centers.

Prior to surgery, three different chest x-rays are are taken to check for visible metastases. Sometimes other long bones are radiographed as well to look for other tumors. If clear, surgery is performed and the affected bone is submitted for to a lab to confirm the diagnosis. Chemotherapy consists of either carboplatin alone, or alternating with doxorubicin.

Amputation without chemotherapy can be performed. This is rarely chosen as it is a major surgery with little increase in life span, although it does increase comfort. Likewise, chemotherapy without amputation is rarely performed due to no measurable increase in survival time.

If a patient with osteosarcoma is not a candidate for amputation (such as a dog with severe arthritis in the other legs), treatment is composed of aggressive pain control, and exercise restriction to try to prevent a fracture from occurring at the tumor site. A drug called zoledronate is commonly used. It was developed for use in women to slow the progression of osteoporosis. It is not a chemotherapeutic agent, but rather it slows down the activity of the cells that decalcify and break down bone, and appears to provide a significant improvement in pain control for our patients. As a bonus, it may slow the progression of the tumor growth, although this has yet to be definitively proven. It is given as an intravenous injection over several hours in the hospital once every 21–28 days.

Other drugs used to control pain include the non-steroidal anti-inflammatory drugs, and a variety of analgesics. These drugs are tailored to the needs and health of each patient.

With pain management alone, the pain can progress within weeks to a couple months to the point where there is no quality of life, and many families elect euthanasia. With the addition of pamidronate the quality of life is significantly better, and therefore it takes longer until the pain interferes significantly. With amputation alone, or pamidronate without amputation, median survival is about 6 months and the end is reached when pulmonary metastases develop significantly. Somewhere between 10–20% of patients live to 1 year, and essentially none make it to 2 years. With amputation and chemotherapy, median survival is about 12 months, with 7–21% of patients surviving to 2 years.

Hemangiosarcoma

A common, aggressive cancer that arises from transformed cells that line blood vessels. The most common form we see is within the spleen.

Hemangiosarcoma is a common, malignant cancer that arises from transformed endothelial cells (the ones that line the blood vessels). Thus, this tumor tends to bleed easily (it makes a lot of blood vessels) and spread easily (through the blood stream). The most common location of the primary tumor is within the spleen, and the most common metastatic sites are the liver and the base of the heart. This cancer is most common in golden retrievers and other large breed dogs.

Typically, there are no signs until the tumor starts to bleed. Then the patient may be very weak, panting, unable, to walk, and have pale gums. These signs are caused by bleeding into either the abdomen or the sac around the heart. It usually happens abruptly.

Radiographs confirm the presence of a mass, and ultrasound is used to determine the location and appearance of the mass. We usually do not aspirate these due to their tendency to bleed. Instead, we head to surgery for removal, followed by histopathology. We cannot tell the difference between splenic hemangiosarcoma and splenic hemangioma (a benign tumor) or hematoma (a bad bruise) based on gross appearance, so we always send out a biopsy.

Surgical removal controls the bleeding, resolving the acute emergency. Chemotherapy historically has been single-agent doxorubicin. There are some new protocols on the horizon.

Splenectomy alone yields survival of less than 6 weeks, with death resulting from the rapid growth of metastatic tumors. Adding doxorubicin increases survival to about 12 months.

Mast Cell Tumors

The most common form is a small mass within the skin. These masses are often very itchy.

A mast cell is a normal part of a pets immune system. It is part of their allergic response to things. Mast cells are therefore in tissues that interact with the outside environment like skin, lungs, and intestinal tract. But, they do also circulate in the blood. When abnormal growth of mast cells occurs they can form a tumor. Mast cell tumors are incredibly common in dogs, 1 in 5 skin tumors, according to Veterinary Partners. In cats, older cats seem to be more affected.

Mast cell tumors are graded based on severity from 1 to 3. One is the best to have because it is the least aggressive and easiest to treat.

Diagnosis is made with a fine needle aspirate. We take a small cell sampling with a needle and look at it under the microscope. We can also remove the mass and send it out for histopathology to find out its grade. This will determine the types of additional treatments recommended by the veterinarian.

Surgery is necessary to remove the tumor. Mast cell tumors are highly invasive and very deep. Depending on the grade of the mast cell the veterinarian may or may not recommend chemotherapy. Mast cells respond best to predisone, lomustine and vinblastine.

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