In the last decade, cancer has become more common in dogs and cats. Pets live longer, and we have better diagnostic tools, which has led to more awareness of the development of cancer in small animals.

What are some common cancers seen in dogs and cats?

Lymphoma is the most common cancer we diagnose in both species. There are also different sarcomas, like soft tissue sarcoma, hemangiosarcoma, osteosarcoma, and a few others, as well as carcinomas, mast cell tumors, leukemias, and myeloma.

What are the symptoms of cancer?

There are no pathognomonic symptoms of cancer, and signs depend on the type of cancer and its location. Vague symptoms like vomiting, diarrhea, anorexia, weight loss, sudden bleeding, swollen lymph nodes, or any combination of these are a reason to investigate but do not necessarily point to cancer right away. Diagnostics such as blood work, X-rays, ultrasound, aspirates, or biopsies are usually performed.

Is cancer preventable?

Cancer is an abnormal growth of cells or tissues, and the cause of most is not known; therefore, prevention is difficult. There is evidence that secondhand smoke increases the risk of some cancers in dogs and cats.

Research shows that spaying reduces the risk of mammary cancer in dogs if done before 12 months of age. Neutering eliminates the risk of testicular cancer. Conversely, there is evidence that spaying and neutering can increase the risk of certain other cancers. Genetic predisposition to some cancers in certain breeds or breeding lines has also been reported.

What is the treatment?

There are many different cancers: some responsive to chemotherapy, some treated surgically, some responsive to radiation, and a few that are not responsive to most treatments. In each case, if we can remove the tumor or even reduce it in size, it makes other modalities (if needed) that much more effective. However, the path we take to cure or improve the quality of life and longevity depends largely on the type and location of the tumor.

It is important to remember that some cancers can be cured, some put into remission, and some only slowed in their progression.

How will my pet feel after chemotherapy?

This is understandably a concern for all pet owners, as our patients' quality of life is the most important aspect. Luckily, dogs and cats typically respond very well and do not have the same side effects as people. If side effects occur, these are mostly GI-related, like vomiting, diarrhea, and anorexia. Myelosuppression (bone marrow suppression ) can also happen, leading to fever. These side effects are transient and usually can be dealt with at home. If another chemotherapy dose is required, we either change the dose or the drug given to avoid the side effects. If the patient still does not do well, chemotherapy is stopped.

Depending on the cancer type, chemotherapy may be lifelong or temporary.

What is the prognosis for a normal quality of life?

This depends on the type of cancer and, in some cases, on its location. Lymphoma, the most common cancer, is very responsive to chemotherapy, and remissions can be as long as 1-1.5 years. After patients come out of remission, chemotherapy can be repeated or a different one used, though the second time around, it is usually less effective. Other cancers, like some carcinomas, may be less responsive or not at all.

What are the risks to other pets or people who are in contact with a pet undergoing chemotherapy?

The true risk is not known, but we do know that the chemotherapy drug is mostly eliminated during the first 3 days post-treatment in feces and urine. Basic hygiene should be maintained. If the patient urinates or defecates on the carpet or floor, it should be cleaned with regular household cleaning supplies. If another pet at home eats the feces of a pet undergoing therapy, some chemotherapy may get into its system. However, the risks posed to that pet after ingestion are not known.

Overall, pets can lead a normal life while undergoing treatment.

Summary

The prevalence of cancer in small animals has led to the development of many modalities for diagnosis and treatment. Nowadays, there are many ways we can treat cancer, whether it is a complete cure or just remission; however, in some cases, if the disease has spread and improvement is unlikely, humane euthanasia may need to be considered. During the treatment process, quality of life is monitored, and treatment is given for as long as the patient is doing well.