Dr. Jeffrey Bryan, board certified specialist in veterinary oncology, has addressed some of the questions submitted in conjunction with our Canine Cancer event sponsored by the AKC Canine Health Foundation (available for on demand viewing):
Genetics
1) Question: Is cancer in different breeds genetic?
Answer: Yes, it appears so. Golden Retrievers have a 1 in 8 lifetime risk of cancer. Boxers are well known to get many cancers. Irish Wolfhounds are predisposed to osteosarcoma. There are many breeds, however, which do not appear to have higher than background cancer risks.
2) Question: Genetic mapping of certain cancers is ongoing. How far has this gone? Example: the United Health Trust in the U.K. has collected DNA samples from Labradors with malignant melanoma. Has this succeeded in identifying a carrier for this cancer type?
Answer: This remains in its infancy. I cannot find the melanoma data published. There is preliminary data that DNA repair defects may play a role in Golden Retriever lymphomas. Other breeds (Rottweilers and the gene MET) have been shown to have specific genes or predisposition to osteosarcoma. There is much work yet to be done in this area.
3) Question: I now have three boxer siblings with lung cancer, with no history that I can ascertain, no smoking, no dog shows in years. Can this be an inherited trait?
Answer: I’m sorry to hear this. There could be an underlying genetic trait in this particular family of dogs. Also, many cancers eventually show up in or arise in the lungs, so these could appear to be “lung” cancer but in fact be several different types of cancer. I’m not sure how much study was done of these dogs’ tumors, so it is hard to say. There could be a common unsuspected environmental exposure that could explain it as well.
4) Question: I have Dobermans and Labradors. I have had 3 Dobes with cancer. #1 stomach, #2 breast tumor that metastasized to the lungs and brain, #3 bone (nasal). #2 and #3 have been within 6 years of each other and within the past 7 years. None of my Labradors have had cancer. Are we dealing with breed or environment as the leading cause? Immune system? None of them has been inbred or even closely linebred. All were extremely healthy otherwise. Thank you!
Answer: Those cancers sound fairly unrelated. I suspect that this is very bad luck in your case. I see far more Labs with cancer than Dobes. I hope your Labs remain healthy!
Lymphoma
1) Question: How long can a dog live with lymphoma, which is in remission, after having a splenectomy to diagnose the cancer, and following limited chemo treatments which were discontinued due to apparent damage to the heart?
Answer: This depends very much on what type of lymphoma it is. Aggressive lymphomas can have very short-lived responses to chemotherapy. Low-grade or indolent lymphomas can have survivals that measure in the years, sometimes without chemotherapy. A thorough biopsy diagnosis by a pathologist with interest in lymphomas can be very helpful.
2) Question: What are chances of remission for gastro lymphoma after treatment? What are the percentages of a remission of greater than 1 year?
Answer: Lymphoma in the stomach of dogs is perhaps better than in the small intestine, but not as good as in the colon or rectum. The latter two sites have been associated with longer survivals (sometimes very long). The stomach and small intestine locations have been historically much worse prognostically. One study found a median survival of only 13 days for dogs with gastrointestinal lymphomas. As with all lymphomas, outcome often depends on grade. Low grade disease can do much better.
3) Question: Please discuss canine lymphoma treatments - both traditional and holistic.
Answer: Chemotherapy is the mainstay of lymphoma treatment. A good discussion can be found in this article. Currently, there are not holistic treatments that have published data showing efficacy. The DNA demethylating properties of green tea extract may be of benefit, but the published data is only in humans and only for low-grade, indolent disease.
Lung Cancer
1) Question: How common is canine lung cancer and what causes this?
Answer: Lung cancer is not very common in dogs. The cause is not clearly known, although small studies have suggested that environmental tobacco smoke may play a role, particularly in brachycephalic (short-nosed) breeds. The association is weak at this time. Some studies have suggested an association between environmental pollutants and lung cancer. Some breeds may be overrepresented as well, although this is not rigorously studied.
Nutrition
1) Question: Does nutrition contribute to cancer susceptibility?
Answer: The answer is almost certainly. However, the mechanisms and critical nutrients are not clearly identified. To date, there is no anti-cancer diet that has been shown to clearly reduce the risk of cancer. Presumably, minimizing environmental exposures to tobacco smoke, lawn treatment chemicals, and feeding fresh vegetables is the best thing to do as we currently understand it.
Cancer Prevention
1) Question: How can we prevent cancer in our dogs?
Answer: Feed fresh veggies! Avoid toxic exposures. Exercise and maintain a good, lean weight.
My pet has cancer ...
1) Question: My 10 year old Boston Terrier has Hepatocellular Carcinoma - she had part of her liver removed but her vet couldn't get it all. Any suggestions for food, supplements, and treatment?
Answer: The good news is that incomplete resection of this particular tumor may not greatly affect outcome. Because it is the job of the liver to metabolize and detoxify, the tumors respond to very few treatments medically. If there is significant tumor left, I would suggest finding a board-certified surgeon to remove the remainder if possible.
2) Question: I have a Giant Schnauzer that has had two toes amputated due to squamous cell carcinoma. Her last amputation was in February but now she is exhibiting symptoms in another toe. I have three questions:
a) Is there significance in it occurring in a new site so quickly? (last time it was 3 years between amputations)
b) If we amputate again, should we also take off the remaining, (so far) healthy toe?
c) Is there some sort follow up treatment we should be doing? The last amputation we caught it very early with very little evidence of the cancer.
Answer: This is hard to answer without knowing your dog. If you are not certain that the new lesion is a recurrence, I would highly recommend a punch biopsy of the area to confirm. Radiation treatments and some new chemotherapy options may help manage the disease without further amputation if such a surgery would reduce her quality of life.
Read more about Squamous Cell Carcinoma
3) Question: 11 year old Doberman with a non-malignant tumor the size of a deck cards located under the abdominal skin just below rib cage and unattached. Skin is shiny, friable, with repeated superficial infections over tumor site. Risks given her age for surgery? How to best treat the overlying skin area to reduce chance of infections?. So far, some success using a stretchy anxiety coat which keeps area covered / tension over tumor tissue, and Silvadene cream - after 2 weeks of antibiotics. Vet says good cardio-pulmonary condition for a surgery.
Answer: Without seeing your dog I can’t advise you very well. I would suggest a cytology sample be collected from the mass to give your surgeon a preview of what must be removed. Some tumors can be removed with relatively narrow margins. Others must have very wide margins to be successful. An opinion from an oncologist may be helpful.
4) Question: Please talk about the rare cancers, such as nose tumors, that sometimes present with no signs until the growth has already spread. With so much contradicting / misinformation to be found on the internet, where do I go to find reliable and accurate resources to help me understand what is going on and to get appropriate treatment? If given the choice, which is more effective, radiation, or chemo, for nose tumors? Thank you.
Answer: The best source of information on these tumors is a board-certified oncologist. A consultation is well worth the money to have the best information for your specific family member. In general, radiation therapy is the mainstay of treating nasal tumors. Rarely, nasal lymphoma or nasal carcinoma might be treated with chemotherapy, but this is not the usual course. Surgery likely is not the best answer in most cases.
