Important note: The following information regarding Tamoxifen as a treatment for rabbits with mammary carcinoma is specific to the two rabbits mentioned below. Tamoxifen has been shown effective when breast cancer has been diagnosed. It may have no effect on other types of cancer. Treatment protocol and dosage may be different for your bunny. Be sure to consult with your vet before using this drug!

RABBIT MAMMARY CARCINOMA AND TAMOXIFEN

I'm lucky! I'm only 15 minutes away from the offices of Dr. Carolynn Harvey, rabbit-savvy vet extraordinaire and Medical Director of the House Rabbit Society. So when I discovered a lump on a mammary gland on Baby, the mascot of the Alameda (California) Animal Shelter (see Baby's Story), it was a snap to hop over and let Dr. Harvey take a look.

Baby was about 8 years old when the tumor was discovered in August of 1999. She had been spayed after she came to live at the shelter at approximately age 6. That's pretty late for a spay, but Dr. Harvey performed a series of tests over a period of about 6 months to make sure Baby was healthy, and our girl came through the spay with flying colors.

When the mammary lump was confirmed to be a tumor, Baby was referred to Dr. Jen Dalmasso for surgery. Chest radiographs (x-rays) were taken prior to surgery which showed no obvious spread to the lungs. The tumor was removed and, once again, Baby did fine. A portion of tissue was sent out for a biopsy, and the pathologist's diagnosis was: Tubular-acinar Adenocarcinoma; i.e., cancer.	Baby
Further testing revealed that some of the cancer cells extended outside the tumor wall and into muscle tissue that had not been excised. Hence, not all cancer cells were removed. In fact, to quote the pathologist, "The likelihood of widespread metastatic lesions is great." Rats! Not good news.

Baby

After the surgery, Baby was placed on a treatment protocol consisting of 1/8th of a 10 mg Tamoxifen tablet, given twice-daily in a raisin. She is weighed once per month to alert us if there has been a sudden weight loss, and every 6 months she receives a complete physical examination in which a blood panel is drawn. No other special considerations are given. She's allowed to eat whatever she wants, she has an excellent appetite and has actually gained a little weight. In fact, the only real change in her lifestyle is that she has "retired" from active shelter life and now lives at home =:3 with the rest of our rabbit gang (although she goes to visit her human friends at the shelter on special occasions).

I am pleased to report that 18 months after the tumor was removed, all tests for recurring cancer have been negative. ::THUMP:: on wood!

About three months after Baby had her surgery, a mammary lump was discovered on a rabbit named Chocolate Bunny, an older spayed female of unknown age. Chest xrays were taken prior the surgery. Again, the lump proved to be a tumor, which was surgically removed by Dr. Dalmasso. Chocolate Bunny was then placed on the same Tamoxifen protocol as Baby and, after more than a year, there are no signs of the cancer returning.

Chocolate Bunny (right) and her mate Magic (left)

In both cases, not having the tumor spread to the lungs probably improved these two bunnies' chances. Chocolate had a "physical" on April 2, 2001 and all test results were well within the ranges of a normal, healthy rabbit. Yay! In May 2001 Baby had her six-month physical exam, with a blood panel and urinalysis, and all the results came back well within the ranges of what's considered "normal" for a 10 year old rabbit. She even gained about half a pound of weight.

Magic (left) with Chocolate Bunny (right)

It is my personal belief that the drug Tamoxifen has been the major reason (perhaps even the only reason) that the cancer has been in remission, although I have no medical proof. However, both Dr. Harvey and Dr. Dalmasso have experience in treating other rabbits with carcinoma using Tamoxifen, and the results have been very positive in controlling the cancer.

Tamoxifen is available by prescription at most pharmacies and from some on-line drug companies. The cost seems to vary greatly. I purchase Baby's and Chocolate Bunny's at Costco, where 50 tablets runs about US $80.

In summary, it appears that Tamoxifen can be highly beneficial to a bunny with certain carcinomas. If your bunny has been so diagnosed, ask your veterinarian about post-surgery treatment with Tamoxifen. If your vet isn't familiar with this drug, suggest that he or she consult with Dr. Harvey or Dr. Dalmasso.

The final chapter of this story can now be written, as both Baby and Chocolate Bunny have passed away.

Chocolate Bunny died on July 12, 2001 as a result of sepsis induced by an intestinal blockage. She passed away quietly with her mate Magic by her side, surrounded by her human friends.  A necropsy revealed absolutely no presence of her cancer returning.

Baby's general health began to deteriorate during the Summer of 2001, and on August 8 we helped her begin her peaceful journey to the Rainbow Bridge. It was the kindest thing we could do for her after a review of x-rays and an Ultrasound, and surgery was not a viable option. Although we had always suspected her cancer would someday return, the necropsy and tissue histopathology revealed that not to be the case. Rather, Baby was the victim of time and old age, and progressive congestive heart failure that affected many of her other organs. Please visit Baby's Photo Album.

It's clear to me that Tamoxifen helped these two bunnies lead longer and happier lives.

Rich
Rabbit Row