R.T.
I'm a breast cancer survivor of 16 years this January 30, 2008. I had the same thing happen to me - gained massive weight on chemo. Went from 105 to 185. Did the Tamoxifen for 5 years too boot. STILL haven't gotten it off. I had been a athelete all my life, even ran track in college in the late 60's/early 70's. Started taking Wellbutrin XL. It's suppose to help. We shall see. The one thing I DO know about the rare weight gain and not being able to get it off is this - I'm the ONLY one of my group of 10 chemo buddies (those of us who sat side by side taking chemo) that was still alive at the 5 year mark! I know of only one other person who did the unexplained massive weight gain, and she survived too. Both of us were in our early 40's when we were diagnosed. SO, the horrible weight gain may be the very thing that helps you survive in the long run. Don't ask me why... just seems to be the case for us other two.
P.S. I just read the other comments to you. Unfortunately, their responses do not address the problem of this massive unexplained weight gain POST mastectomy after all the surgeries, drugs, treatments- and the "normal" stuff does not work. It is NOT a normal weight gain, as YOU and I BOTH know. My diet has not changed from when I was 105 pounds. But something about the weight gain, contrary to conventional wisdom, keeps the cancer from re-occurring. That is the blessing to count. Wellbutrin XL is an old antidepressent that CAN be used to boost up the metabolism. I've just started it, taking 300mg. You might ask your doctor to try it, however, WARNING! DO NOT ACCEPT THE GENERIC OF THIS DRUG, AS OF NOVEMBER OF 2007 MSNBC POSTED AN ARTICLE ABOUT THE GENERIC NOT BEING THE SAME AND CAUSING ADVERSE PROBLEMS. You can probably Google a search on the problems with the generic of this drug. If you want to follow up with me on this, ###-###-####.