Spaying at age 10 to combat cancer

Question
Hi, Dana.  I wrote to you last month regarding my pet
rabbit, Mina.  She had a lump on her tummy, which we had
removed and biopsied.  She's doing well, but the biopsy
results indicated that the lump was a cancerous tumor.  The
vet said the tests indicate that it seems they got all the
current lumps/tumors that were there.  However, as this is a
hormonal responsive type of cancer, spaying is the best
option to prevent any recurrence.

I know it's bad that she hasn't been spayed.  I was young
when I first got her, and the vet I had her to back then
didn't recommend spaying as "surgery is so risky for
rabbits" (his words).  The vet I use now said that he is
willing to do the spay, but because of her age, I should be
aware that she may not live much longer anyway, and that the
spay isn't a guarantee of no recurrence of the cancer.

I have two questions for you about this.  First, since she
just got the tumor removal surgery two weeks ago, how long
should I really wait before subjecting her to more surgery?  
She had two tumors removed that day.  One, low on her tummy,
near her back leg, and the other in her chest cavity.  

Second, is it foolish to want to get her the surgery,
despite her age?  She's always been in fantastic health
aside from this, and still has a lot of energy.  She's
eating, defecating, and sleeping normally, and is pleasant
with no signs of pain.  I feel like she could recover from
this and may have years to come.  She is 10 1/2 years old,
female, and I believe she's a dwarf breed--nobody has ever
really identified her breed for me, but she's just under 3
pounds and has never grown any larger, and her colorings
make her appear like a wild rabbit.  (I wonder if I provided
a picture if you'd be able to suggest what breed she might
be?)  

What is your advice on this?  I want to do all I can for
her, and I'm just not ready to give up on her!  However, if
surgery would only make her suffer needlessly, I wonder if
it's the best option.  Thank you again for all your help!  
Your advice has been very comforting and helpful to me
during this tough time!

Answer
Dear Jennifer,

This is a very tough call.  I'll try to analyze this as if she were my bunny.  What would I do?

On the one hand, while the vet did get all the tumors, there is still the possibility that a metastatic cell may have escaped or already moved to another area of the body that's not so operable (e.g., lungs).  If that's the case, then spaying her will not really make much difference.  

On the other hand, if these cancer cells are estrogen sensitive, and if her ovaries are still producing a goodly amount of estrogen (which is not at all a given, at her age; while rabbits don't undergo menopause the way humans do, a 10 year old rabbit's ovaries are surely not as productive, hormonally, as a younger rabbit's are.), then removing the ovaries would remove the stimulus some of these cells need to proliferate.

One option might be to consider chemotherapeutic drugs used in treatment of human breast cancer (e.g., tamoxifen), though I would have no idea what dosage would be appropriate for a rabbit.  But this would obviate the need for surgery, if her ovaries are not producing much estrogen to begin with.

Another option would be to just wait and see.  If she develops new tumors, then you can decide at that time whether to remove them, and since she will be under anesthesia for that, anyway, also have her spayed at the same time.

I'm not sure what I'd do, but at this moment, I'm leaning towards that last option.

Never an easy call when it's something like this.  But maybe discuss these options with your vet and get a medical opinion about them.

Sending many healing thoughts....


Dana