By Arnold Plotnick, MS, DVM, ACVIM
Cancer in Cats
“I’m feeling a lump in Annie’s abdomen”.
As a veterinarian, I’m sometimes forced to give unwelcome news.I could not have uttered words more devastating, however, than those just delivered to Christoph and Ellen Franzgrote.A year ago, they watched their cat Mia succumb to lymphosarcoma, a cancer of the lymphoid tissues.Mia couldn’t abide her chemotherapy and quickly surrendered to the disease at the age of five.Today’s routine wellness check on Mia’s daughter, Annie, yielded an abdominal mass.
The prevalence of feline cancer is increasing.Advances in veterinary medicine have allowed cats to live longer, and cancer is generally a disease of older animals. This is the fateful price cats must pay for living longer.
Cancer is unrestrained cell division and growth.Normally, cell division is tightly regulated.When a single cell undergoes a series of genetic mutations, cancer may arise, causing cell division to become unregulated, resulting in a tumor.While the cause of most cancers remains unknown, environmental agents can induce cancerous changes in cells, such as viruses, chemicals, radiation, and some hormones.The effects of these agents can accumulate over time, explaining why cancer more commonly affects older animals.
Another word for cancer is neoplasia (“new growth”), and tumors are sometimes referred to as neoplasms.Tumors are classified as benign or malignant.>Benign tumors remain at their original site.Malignant tumors can invade surrounding tissues and gain access to the bloodstream or lymphatic vessels, and then be transported to nearby lymph nodes or other part(s) of the body.This is called metastasis, and is commonly how cancer spreads.The word cancer generally implies malignancy.While benign tumors are generally less worrisome and malignant tumors are more troubling, this distinction isn’t always clear-cut.A seemingly benign tumor may behave malignant clinically, impinging on nearby structures and becoming impossible to remove or treat.
Cats are susceptible to a variety of cancers.Among the most devastating are lymphosarcoma, squamous cell carcinoma, and mammary (breast) cancer.
Lymphosarcoma is a cancer arising from lymphoid tissues involving any organ.Affected cats ranges, on average, from 2 to 6 years, although any age cat is susceptible.Infection with the feline leukemia virus increases the risk of developing lymphosarcoma.This is especially true of younger cats.Older cats that develop lymphoma are less likely to be concurrently infected with the feline leukemia virus.Lymphosarcoma is often categorized by anatomic location.The five types are mediastinal (involving structures inside the chest), alimentary (digestive system), multicentric (the lymph nodes), leukemic (the bloodstream), and extranodal (other organs, such as the kidneys, eyes, nervous system, nasal cavity, and skin).
In cats, the most common sites are the gastrointestinal tract, the mediastinum (structures in the chest such as the thymus and associated lymph nodes), the liver, spleen, and kidneys.Fortunately, lymphosarcoma is fairly responsive to chemotherapy.
Squamous cell carcinoma (SCC) accounts for 15% of all feline skin tumors. These tumors usually involve light or unpigmented skin. Sun exposure increases the risk of developing SCC. Solar-induced SCC is referred to as “actinic” SCC. The most common locations are the hairless area of the nose, the eyelids, and ears. Older cats are at higher risk; the mean age for affected cats is 12 years. Siamese cats, with their pigmented skin, are less likely to develop SCC than other breeds. SCC of the skin is often amenable to treatment. Dr. Tim Rocha is a board-certified veterinary oncologist in New York City who has had good success treating SCC of the skin. “Except in advanced cases, we have several therapeutic options that all have good to excellent success rates.Surgery, radiation therapy, and intralesional chemotherapy (where the drug is injected directly into the tumor) have all been shown effective in treating this cancer”, says Dr. Rocha. SCC may also affect a cat’s mouth. This is often disastrous, as oral SCC is much worse than the skin form. “Unfortunately”, says Dr. Rocha.“95% of these oral SCC cases are diagnosed only after the cat shows dramatic changes in appearance, such as swelling of the jaw or face, severe weight loss, or blood in the mouth”.
Treatment for oral SCC is often unrewarding.“It is sad that we have yet to identify any treatments that are reliably helpful.”Surgery offers the best chance for survival, but most of the time it has progressed too far. “If a SCC is removed surgically in it’s entirety, a cat may become one of the rare 5% of cats that beat this diagnosis”, says Dr. Rocha.
Mammary tumors tend to develop in older cats. They account for 17% of neoplasms in female cats.Spaying dogs before their first heat lessens the risk of future mammary tumor development, and this also holds true for cats.Rarely, male cats will be affected.In cats, the behavior of mammary tumors is very different compared to dogs.While roughly half of canine mammary tumors are malignant, at least 80% of feline mammary tumors are malignant.Siamese cats have at least twice the risk of developing mammary tumors compared to other breeds, and they tend to be affected earlier, reaching a plateau at 9 years of age.More than half of affected cats show multiple gland involvement.Unfortunately, mammary cancer may spread to the lungs quickly, making the prognosis guarded or poor.Surgery is the best treatment option for feline mammary tumors. Dr. Kathy Kazmierski, a veterinary oncologist at Garden State Veterinary Specialists in New Jersey, says that the most important prognostic factor for survival is the size of the tumor at diagnosis and removal.“Tumors that are less than 2 centimeters big are much better than those that are 3 centimeters or greater”, she says.“Follow-up chemotherapy is often recommended”, says Dr. Kazmierski, “but there are not enough cases studied to know if that offers a true survival benefit”.
To make a definitive diagnosis of cancer, tests must be performed.Blood work, x-rays, and ultrasound provide a great deal of information, but ultimately, most cases require a biopsy to confirm the diagnosis.
Blood tests on Annie Franzgrote showed no cancer cells in the circulation, and she tested negative for the feline leukemia virus.Further tests were needed to characterize the abdominal mass.X-rays were taken, and the results were highly suggestive of an intestinal tumor.
Once cancer is diagnosed, there are three common treatment options:surgery, chemotherapy, or radiation.Surgery affords the best chance a cure, by removing the affected tissue.Surgery is curative only if the cancer hasn’t already spread and if the affected area can be removed completely.For cancers like leukemia, which involves the bloodstream, surgery is obviously not an option.
Radiation is an option for localized tumors that cannot be treated surgically, or were treated surgically but all cancerous tissue couldn’t be removed.Radiation injures rapidly dividing cells, such as cancer cells.When irradiated, cancer cells can no longer divide and spread, so they die.Some cancers are very susceptible to radiation treatment, while others are resistant.
Chemotherapy is another common option, especially for cancers involving many body sites, or sites that aren’t disposed to surgery or radiation.While many veterinary chemotherapy drugs are exactly the same as those used in humans, they’re not given with the same expectations.Chemotherapy for animals is not intended to be curative.The goal is to reduce the number of cancer cells and slow the progression of disease for as long as possible, while maintaining good quality of life.As such, most cats tolerate chemotherapy very well.Chemo drugs are potent, however, and cats must be monitored for side effects such as vomiting, diarrhea, and poor appetite.Generalized hair loss is uncommon, but shaved hair is slower to grow back, and cats may lose their whiskers.
For Annie, surgery afforded the best chance of a cure.At surgery, a discrete tumor affecting the small intestine was discovered. A nearby lymph node was enlarged.The tumor was removed, and the lymph node was biopsied.Annie recovered uneventfully.Two days later, the pathologist’s report arrived: lymphosarcoma, with the disheartening news that cancer cells were detected in the lymph node.The tumor had spread.Surgery alone wasn’t going to be effective.
The Franzgrotes elected not to attempt chemotherapy, due to Annie’s nature.“Annie was very sensitive, and the idea of her living in fear when we approached her was unacceptable”, says Christophe.After much discussion, it was agreed that Annie would live the remainder of her life at home, and euthanasia would be considered when the quality of life was no longer satisfactory.“We concentrated on lavishing her with care, giving her anything she desired”, notes Ellen. Annie did well for several weeks until the cancer spread to her kidneys, causing them to fail.With her condition rapidly deteriorating, the Franzgrotes elected to put her to sleep, 10 weeks after the diagnosis.
The decision to euthanize a pet with cancer is often the most difficult choice a pet owner makes.Owners must strike the delicate balance between waiting too long and having their cat suffer or be in pain, and deciding too soon and feeling as if they’ve deprived themselves and their cat even a day or two of reasonably comfortable life.Frequent consultation with the veterinarian and clear communication between family members often leads to the proper determination as to when it’s time to bid farewell.
The single most important prognostic factor for successful treatment of cancer is early detection.As veterinarians and cat owners develop an increasing awareness of cancer, earlier detection becomes more likely.Unfortunately for Annie, her cancer had spread before it was detected.
As luck would have it for the Franzgrotes, our hospital stumbled upon a somewhat sickly stray kitten.Christophe and Ellen spied little Roopoo as they passed by our front door, and it was love at first sight.Once nursed back to health, they took him home, where he instantly clicked with Annie’s forlorn housemate, Lucie.They now spend their days wrestling and napping together.“After our past heartache, nothing gives us more satisfaction than the company of these two happy and healthy cats”.
What to do if you feel or spot a lump or bump on your cat
Petting and stroking your cat isn’t just about affection. It’s also a good way to monitor your cat for the development of lumps and bumps. Lumps on the back and the legs are more easily felt.Conscientious pet owners should feel all over the cat, especially in uncommon areas like the mammary glands, the mouth, and the underside of the neck. If you feel a lump or bump on your cat, take note of several things:
- Texture (soft or firm)
- Sensitivity (does it bother your car when you touch it)
- Other characteristics (Is it ulcerated? Oozing? Bleeding? Associated foul smell?)
While the vast majority of lumps and bumps are harmless, it takes a professional assessment to be sure. In general, benign lumps grow more slowly and often have well-defined edges to them. Ifyou choose to monitor the lump yourself, be vigilant. All big tumors begin as small tumors. Don’t overlook them. If the lump exhibits any significant changes – a sudden increase in size, texture, or any other characteristic – see your veterinarian immediately.
According to the Veterinary Cancer Society, there are some common signs of cancer in animals that owners can look for.
- Abnormal swellings that persist or continue to grow
- Sores that do not heal
- Weight loss
- Loss of appetite
- Bleeding or discharge from any body opening
- Offensive odor
- Difficulty eating or swallowing
- Hesitation to exercise or loss of stamina
- Persistent lameness or stiffness
- Difficulty breathing, urinating, or defecating
Other signs, such as pain, fever, anemia, drinking too much water, producing excessive urine, and ravenous appetite may also be signs of cancer, depending on the specific tumor and the effects it has on the body.