Cancer and Diabetes


What is Cancer?
Cancer is the uncontrolled growth of cells. The cancerous cell mass is called a tumor or neoplasm. Cancers can be harmless (benign) or malignant. Cancer cells grow more rapidly than normal, healthy cells. Of the cancerous cells, benign tumors tend to grow less quickly, remain localized to a distinct mass, and can be cured by surgical removal. Malignant tumors tend to grow rapidly, invade surrounding tissues, spread to other parts of the body (metastasize), and are not as easily removed by surgery.

Most tumors result from unknown causes. Other possible causes of cancer include exposure to cancer-causing agents such as ultraviolet radiation (sunlight), x-rays, cigarette smoke, or viruses (feline leukemia virus, feline sarcoma virus).

From the American Veterinary Medical Association:

  • abnormal swellings that continue to grow
  • sores that do not heal
  • lumps in the breast area
  • offensive odor
  • difficulty breathing
  • difficulty eating or swallowing
  • difficulty urinating or defecating
  • loss of energy or reluctance to exercise
  • loss of appetite, weight loss
  • lameness or stiff movement
  • bleeding or discharge from any body opening (mouth, nose, urinary tract, vagina, or rectum)

Diagnosis and Testing
Health history, clinical signs, physical exam, and X-rays may identify the presence of a tumor, but definitive diagnosis of cancer requires identification of the tumor cells under a microscope. The cells can be obtained during a biopsy, where a small sample of the cells is collected. A biopsy is very important. Even experienced veterinarians cannot always tell the difference between a developmental problem, inflammatory condition, and a tumor on the basis of a physical examination alone.  This is especially true with a small tumor. Since proper diagnosis and treatment are so important in cancer, and a misdiagnosis could either delay treatment or result in unnecessary treatment, the benefits of a biopsy and microscopic identification of the suspected tumor cells far outweighs the very small risks associated with performing a biopsy. A small tumor may be biopsied and removed all at once.  This is called an excisional biopsy because the tumor has been excised (removed) from the body. A larger tumor may require an incisional biopsy where an incision is made and a small edge of the tumor is removed. Another biopsy technique is called fine-needle aspiration, where a needle is inserted into the tumor and a sample of cells are drawn into a syringe. Biopsies are often done under anesthesia and ultrasound may be used so the doctor can guide the needle to the proper location. 

Since prompt treatment is critical, a "let's wait and see what happens" approach is no longer considered acceptable when a lump is found. If there is even the smallest chance that the lump could be a cancerous tumor, a biopsy should be performed. You don't want to panic every time you feel a small lump on your pet, but if the lump has grown quickly, is changing, or is somehow unusual, you should get it checked out. Older dogs commonly have benign fatty lumps (lipomas) and your vet can examine them and tell you what they are. 

The specimen collected during a biopsy is sent to a pathologist who identifies the type of tumor, whether it is benign or malignant, and describes different characteristics of the tumor cells. These characteristics help in determining how advanced the cancer is, whether it is localized or has invaded other tissues, and how well your pet may respond to treatment.

Treatment methods
Like most other diseases, early detection and treatment are very important. Cancer treatments vary depending on the type and stage of cancer, and there are far too many specific treatments to describe here. We've described the general forms of treatment below. Multiple forms of treatment are often used. 

surgery: surgical removal the the tumor and other involved tissues.

radiation therapy: some form of radiation is targeted to the cancer cells and is believed to damage the DNA and interfere will cell replication.  For example, hyperthyroidism in cats is often treated with radioactive iodine, which is taken up by the overactive thyroid gland and destroys it.

chemotherapy: administration of a drug that destroys tumor cells. These drugs are called cytotoxic agents. Anti-cancer drugs  have various side effects because they do not act just on the tumor cell, but on all cells. They tend to act on rapidly growing cells (tumor cells), but healthy cells of the bone marrow and digestive tract are also rapidly growing cells and they may be effected. Side effects in pets are usually much less severe than you hear about in humans (vomiting, hair loss) and most pets tolerate chemotherapy very well.  Blood tests to monitor CBC, liver, and kidney function are often performed during the course of chemotherapy to be sure the non-target cells are not being damaged too much.  

cryosurgery: freezing the tumor tissue to death, usually using liquid nitrogen. Tumors that may be treated with cryosurgery are usually on the surface of the body and include those involving the skin, oral cavity, ears, and eyelids.  

hyperthermia: heating tumor cells to kill them or their blood supply.  Hyperthermia is often used with other treatments such as radiation therapy or chemotherapy.  

laser therapy: lasers (powerful light sources) can be used as a type of scalpel to separate the tumor tissue from healthy tissue.  The use of a laser reduces blood loss and contamination of the surgical area, and decreases the potential for spreading tumor cells. Laser therapy may also be used in a form of treatment where first a drug is given that sensitizes the tumor cells to light, then the laser is used to irradiate the tumor with light, which activates the drug and the tumor tissue is destroyed. 

immunotherapy: boosting the immune system so the body can better respond to destroy the tumor tissue.  It is usually used with surgery, chemotherapy, or radiation therapy. Tumors treated by immunotherapy are usually small and localized.  

Special Considerations for Treating Diabetics
The decision to treat a cancer is a difficult one, but just because your pet is diabetic does not mean cancer therapy should not be considered. Many diabetic pets have successfully undergone treatment for cancers.

Depending on the type and stage of cancer, treatment may cure your pet of cancer. In other cases, treatment may not be able to cure your pet, but may be able to alleviate many of the problems associated with the cancer, improve your pet's quality of life, and give you many more years with your pet. 

The long-term prognosis, overall health of your pet, age, severity and duration of debilitation that will result from treatment, post operative care, and cost are all factors that should be considered when deciding whether or not to have your pet undergo cancer therapy. 

When you discuss these things with your vet, be sure to keep in mind that your pet has diabetes. Minimizing stress and keeping the diabetes as well controlled as possible will help your pet's healing process. If there is a loss of appetite or decreased activity during treatment and recovery, your pet's insulin dose may need to be decreased.  

Questions for your vet

  • If your pet is having surgery, what will you have to do about feeding and insulin the night before surgery?
  • After surgery, how long of a recovery time is typical?  Will someone be monitoring your pet's bg to be sure it isn't too high or low?
  • What types of side-effects should you expect from the treatment?
  • How severe are the side effects?  
  • What do you do if the side effects seem severe or if your pet's diabetes becomes very uncontrolled?
  • Will the chemotherapy drug or other treatment damage the pancreas and make the diabetes worse? This may be a side-effect you have to accept, but it would be nice to know in advance if this is something you should expect. 
  • If you want to use dietary supplements, herbal remedies, or any other non-traditional therapies during the treatment or recovery period, be sure to ask your vet if they will effect the diabetes or the cancer treatment.

Experiences with diabetes and Cancer

If you would like to share your pet's experience with diabetes and cancer, please write brief story (~1/2 page or 500 words). Include your e-mail in your story if you want people to be able to contact you from the website.     Email your story 

There are several excellent resources on the Internet for pets with cancer


Pets Living With Cancer: A Pet Owner's Resource by Robin Downing, DVM.  Paperback - 142 pages  Dr. Robin Downing, a veterinarian who had to confront a cancer diagnosis in her dog, Murphy, found there was no one source for all the questions she faced. Her book is a complete guide to treatment and care. Written with the positive but realistic view that cancer does not always mean death, she answers many questions in a comprehensive and caring manner. There is a glossary of terms common to cancer discussions and treatment. 
kosins.gif (10530 bytes) Maya's First Rose: Diary of a Very Special Love by Martin Scot Kosins (August 1996).   From the days of Maya's youth to the sad and courageous years of her decline, this exhilarating memoir captures the magical bond that can grow between humans and animals. 
If you know someone who is caring for a "special needs" pet or who has recently lost a pet, this is a wonderfully inspiring book  that you can inscribe.


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Updated January 2004
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