The word ‘cancer’ strikes fear in all of us; however, with new advances in veterinary technology and chemotherapy, many pets are living longer with a greatly improved quality of life. Successful cancer treatment often lies in early detection and identification. Early detection can be difficult at times, as cancer may not only present itself as a lump on the skin, but may arise inside the body. If left undiagnosed, the disease may not be noticed until clinical symptoms develop.

In order to identify the type of cancer, aspirates and biopsies are performed. Once the cancer is identified, it is “staged.” This is accomplished by lymph node sampling, ultrasonography and / or radiology examination.

Treatment depends on the type and location of the cancer. If possible, surgical removal of the tumor is performed. Some types of cancer are responsive to chemotherapy, which include a variety of oral and injectable medications. Dogs and cats tend to tolerate chemotherapy well and rarely develop side effects that are seen in humans. Prior to treatment, blood and urine tests are performed to asses the overall health of your pet.

Chemotherapy is offered at Atlantic Coast Veterinary Specialists. Our primary goal is to obtain a cure. If a cure is not possible, the goal of chemotherapy is to provide a better quality of life for your pet. We recommend treatment only if it is appropriate for your pet.

Aim of Chemotherapy

The goal of the clinicians at Atlantic Coast Veterinary Specialists is to prolong your pet’s life but more importantly, to maintain a good quality of life for them while they are undergoing treatment for cancer.  Although we use similar drugs to those used in treating people with cancer, we don’t use the high doses needed in more intensive protocols for human patients.  The side effects that our animal patients face are therefore much reduced or often non-existent.

What is Chemotherapy?

Technically, chemotherapy means the use of a drug to treat any illness, but in recent years the term chemotherapy has been used primarily to describe anti-cancer drug treatment.  Chemotherapy can also be used in conjunction with surgery and/or radiation treatment.  Over the years, chemotherapy has proven to be helpful in the treatment of several different types of cancer in dogs and cats.

How does Chemotherapy work?

Cancer can generally be defined as a rapid, uncontrolled growth of cells. Anti-cancer drugs interfere with the ability of rapidly-growing cells to grow and multiply. In many cases, a combination of different drugs working in different ways is the most effective method to kill the cancer cells.  Unfortunately anti-cancer drugs cannot usually discriminate between cancer cells and normal body cells, and so systemic chemotherapy can affect normal cells – especially those found in the bone marrow and gastrointestinal tract.  Most normal cells, however, are better able to recover and repair themselves than cancer cells.

How is Chemotherapy given?

Most anti-cancer drugs are given either by mouth (orally) or by injection. Some drugs need to be injected into a vein and reach the blood directly, while others can be injected into the muscle or under the skin and are absorbed more slowly into the blood stream.

How long will your pet receive Chemotherapy?

The length of time and frequency of drug administration will depend on the type of cancer and how well the treatment is tolerated by the patient.  Treatment may be given daily, weekly, or monthly, and sometimes the time between treatments is tailored to the individual patient.  On occasion, treatment may be given in cycles that may include rest periods where no treatment is given.  In this way patients have a chance to build healthy new cells.

Are you at risk of exposure to these drugs?

  • For orally administered drugs, as with all medication, it is important that capsules or pills are kept out of reach of children, in child-proof containers.  Most oral drugs have a protective coating, but we recommend that you wear gloves when handling these medications.
  • It is also important to avoid unnecessary contact with the urine and feces of animals receiving chemotherapy, especially for the first week after the drug is given.

This really just involves normal sensible hygiene precautions.  If your dog or cat has an accident in the house, wear gloves to clean it up – cat litter can be a useful absorbent material to use on urine.  Then thoroughly rinse the exposed surface after the waste is cleaned off.

Will your pet experience any side effects?

We will always try to choose the drug doses and combinations likely to cause the least side effects while still giving the best therapeutic advantage possible for your pet.

Steroid drugs often have a role and these may be given at high doses in the early stages of treatment.  Side effects that you may notice include your pet drinking more, and they will need to have free access to water and frequent opportunities to urinate.  The appetite often increases and some dogs will appear to pant more.  These side effects are mild, reversible and improve as the dose is tapered.

Please monitor your pet during treatment and feel free to contact us if you feel he or she seems ill or if you have any questions or concerns.  Your pet may need to be seen by us or your regular veterinarian (or their emergency service) if they experience severe side effects.

The following are potential adverse reactions to treatment and appropriate actions:

Fever

Normal dog and cat temperatures tend to be about 100°F to 102.5°F (37.8°C to 39.4°C).  Most dogs and cats with a high temperature are depressed and refuse to eat.  If their temperature rises significantly, especially if your pet is very lethargic or has any blood in his/her feces, it may be necessary for a vet to prescribe antibiotics and possibly intravenous (IV) fluid therapy.  Once you have begun a course of antibiotics you will typically need to complete the course of treatment that was prescribed even if the condition improves rapidly, as it often will.

Vomiting

Vomiting once or twice (without any other signs or fever) should be monitored, but does not usually require treatment.  If it continues for more than 24 to 36 hours, or if your pet vomits more than 4 to 6 times per day, please contact a vet.  Withdrawing food and water for a few hours may be helpful; obviously water should not be restricted for any longer.  Water should be reintroduced first and if your pet can drink without vomiting then you can offer small amounts of bland food such as home-cooked fish or chicken for 1-3 days before gradually returning to the normal diet.

Frequent vomiting, or vomiting in conjunction with a high temperature where your pet clearly feels unwell, may require hospitalization and further treatment including intravenous (IV) fluid therapy and drugs to control nausea.

Diarrhea

Diarrhea without vomiting or fever can usually be managed with a bland diet (fish or chicken with some white rice or potato) until stools are normal and then gradually switching back to the food you normally give.

Cystitis

Signs of bladder discomfort (straining to urinate, urinating small amounts frequently, blood seen in the urine) may occur occasionally after cyclophosphamide treatment.  Please call us if you see any of these signs.  In order to reduce the risk of cystitis developing, please make sure that your pet has plenty of fresh water available at all times, and has frequent opportunities to urinate on the day of treatment and for a few days afterwards.

Hair Loss

Only dogs with continually growing hair coats (e.g. Poodles, Old English Sheepdogs, some Terriers) tend to lose significant amounts of hair although other breeds can sometimes be affected and cats may lose their whiskers.  Hair coats will often return when treatment is finished, or with a decrease in frequency of chemotherapy administration, but it may take some time for full recovery; a different colour and texture of hair may re-grow.

Heart Disease

Doxorubicin is a potent anti-cancer drug which has been associated with causing heart disease with long-term use in certain dogs, particularly some large-breed dogs.  This side effect is not a major issue in most dogs that receive a limited amount of doxorubicin in their lifetime.  However, in dogs with pre-existing heart disease or those that receive a lot of doses, doxorubicin may lead to increased risk.  If your dog is identified as having a form of pre-existing heart disease that is likely to cause problems if doxorubicin is used, we will discuss this in detail with you.  This does not appear to be a problem in cats; cats need to be monitored for kidney problems.

Talk to us about your concerns

The above list of potential side effects of chemotherapy may appear worrying, but please realize that this includes the common side effects of a variety of drugs used to treat many different tumours.

We hope that your dog or cat will feel well throughout the time that he/she is receiving chemotherapy, or perhaps just have one day after the treatment when they are just a bit off-color (loss of appetite, slight nausea).  Unfortunately though, every patient is different in how they respond and we have to balance giving them as much drug as possible (to increase the chance that the cancer will respond well) with keeping them feeling well.

This means that we have a ‘starting point,’ or a drug dose that the majority of patients tolerate well, but if you feel that your dog or cat is unwell during treatment, contact us and in many cases we will likely advise a lower dose the next time that your pet is due for chemotherapy or possibly change the type of drug that we give to decrease the chances of unacceptable side effects. Every individual is different and we rely on owners, who know the dog or cat best, to let us know how the pet is responding to the drugs.

If you have any questions at all, please contact Atlantic Coast Veterinary Specialists at (631) 285-7780.

References

Hayes, A. (2005) Safe use of anti cancer chemotherapy in small animal practice. In Practice 27, 118-127