Bone Cancer in Dogs


Bone Cancer in Dogs



Please discuss all information with your vet.

Cyclophosphamide is a chemotherapy drug given as part of the metronomic protocol for dogs with bone cancer. It is a pill administered on a varied schedule according to different protocols, ranging from once a day to once a week. It functions both as an anti-cancer drug and as an immunosuppressant, which can cause significant side effects. Your vet may recommend that you use gloves when handling the pills or collecting your dog’s urine or feces.

Potential Side Effects of Cyclophoshamide

Hemorrhagic Cystitis

The most important side effect of cyclophosphamide is hemorrhagic cystitis, which means “bloody inflammation of the bladder.” This is caused by the breakdown products of the drug. The longer the breakdown products are in contact with the bladder, the higher the likelihood of this side effect. For this reason, the following guidelines should be followed:

The medication should be given as a single dose in the morning.

Your dog should be encouraged to drink plenty of fluids increasing fluid intake.

Your dog should be encouraged to urinate frequently during the day, which may mean more frequent potty breaks than usual.

The veterinarian may prescribe a “water pill” (diuretic) to be given on the days that the cyclophosphamide is given. This will dramatically decrease the risk of hemorrhagic cystitis, because it will increase the volume of urine and trigger your dog to drink more fluids.

The easiest way to check if your dog has hemorrhagic cystitis is to inspect the urine. This can be done several times a week, by holding an aluminum pie plate under him/her while urinating. If the urine appears bloody or dark, do not give any further doses of cyclophosphamide and contact your veterinarian immediately. If the urine appears normal, check with your veterinarian periodically for a urinalysis test which can show small amounts of blood in the urine not visible to the naked eye. It is also important to check for urine infections, which can also cause blood in the urine.

Reduction in the Number of White Blood Cells (Neutropenia)

There are various types of cells in the blood. The decrease in the number of infection-fighting white blood cells is known as neutropenia. Chemotherapy can affect the bone marrow’s ability to produce cells. As a result, neutropenia may occur 10-14 days after chemotherapy. Neutropenia alone is not a danger to your pet. However, your pet’s ability to fight off infection is impaired by neutropenia. Therefore, prior to each treatment, your pet will get a blood test called a complete blood count (CBC). Should your pet 

have a significant reduction in the number of white blood cells, your veterinarian may wish to perform periodic blood tests, and/or prescribe antibiotics to protect your pet from infection and delay the next dose of chemotherapy until the count comes back to normal.  Less commonly, cyclophosphamide can affect the platelets and the red blood cells. These cells can also be monitored by the complete blood count (CBC).

Stomach or Intestinal (Gastrointestinal) Discomfort

Dogs can experience some form of stomach or intestinal discomfort within a week after a chemotherapy treatment. Your veterinarian will prescribe medication to try to prevent or treat the discomfort. Ask your vet about giving the medication even if there are no overt signs of discomfort. Below are listed some suggestions to discuss with your doctor.

Upset Stomach (Nausea)

  • If your pet begins to show any signs of upset stomach (drooling, smacking lips) or loss of appetite, administer the medicine your doctor prescribed for nausea.
  • Offer ice cubes every few hours.
  • After 12 hours, feed your pet small, frequent meals instead of one large meal.
  • Call your veterinarian if you have concerns, or if the condition persists for more than 24 hours.


  • Do not give your pet any food or water for 12 hours.
  • After 12 hours, offer your pet ice cubes, then water, then small bland meals.
  • Call your veterinarian if you have concerns, or if the condition persists for more than 24 hours.

Loss of Appetite

  • If your pet begins to show any signs of upset stomach or loss of appetite, administer the medicine your doctor prescribed for nausea.
  • Offer your pet four small meals a day.
  • Add warm broth, animal fats, and favorite foods to increase flavor and appeal.


  • If your pet begins to show signs of diarrhea, administer the medicine your doctor prescribed for diarrhea.
  • Keep water available at all times.
  • If your pet is also not eating, offer chicken or beef broth.
  • Call your veterinarian if you have concerns, or if the condition persists for more than 24 hours.

Kidney Damage

Kidney damage can result from chemotherapy drugs. Your dog’s kidney function should be checked by performing kidney function

blood tests and urine tests prior to each treatment. If any abnormalities are detected, intravenous or subcutaneous fluids may be necessary to correct the problem and the cyclophoshamide may not be prescribed until the tests return to normal.

Allergic Reactions

Allergic reaction to chemotherapeutic agents is rare, and not a problem you will have to treat at home. Should your pet have an allergic reaction to cyclophosphamide contact your veterinarian immediately.

Hair Loss (Alopecia)

Pets who receive cyclophoshamide rarely lose their hair and, if they do, they are not bothered by it as much as people are. In most pet animals, hair does not grow continually throughout their lives like it does in people. Therefore, hair loss in pets is rare. Exceptions are certain breeds of dogs, such as poodles, old English sheepdogs and other breeds whose hair grows continually. In general, if your pet needs to visit a groomer periodically to be clipped, then your pet may experience some degree of hair loss as a result of chemotherapy. Please ask your veterinarian about the possibility of hair loss.

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