Reoccuring breast cancer 5 years after masectomy and use of Tamoxifan(tamoxifen)

Five years ago this past August my mother was diagonosed with breast cancer.  She had a radical masectomy and the doctor opted for the use of Tamoxifan (tamoxifen) rather than chemotherapy.  For the past five years she has gone cancer free and was taken off the Tamoxifan (tamoxifen) in August.  Over the past two years she has had reconstructive surgery to form a new breast with her own tissue and in order for the breast to match she had her remaining breast lifted.  My mother had a mamogram (mammogram) in September which indicated no lumps however, at the first of October she found a lump in the cancer free breast.  The lump grew and the doctor removed two lumps this past Friday and we are waiting for the results.  Can you explain to me why they did not keep her on Tamoxifan (tamoxifen) longer than five years as a precautionary measure and how in such a small amount of time since going off the medication lumps appeared?

[CCF-RN,MSN-JS]

Dear Murraycal, At present, the available data supports the stopping of tamoxifen at 5 years.  Some studies have shown that continuing beyond 5 years of therapy patients had a greater risk of recurrence of the breast cancer.  While other studies showed that continuing beyond 5 years may delay relapse in ER-positive patients; however, there was no difference in overall survival.
So based on this information and data from other studies 5 years of Tamoxifen was settled on as the standard.

It is difficult to say why these lumps appeared in this short amount of time, it could be there was something in the process that did not show up on the mammogram, or possibly these are cysts that may have appeared because of changing hormone levels since being off of the Tamoxifen. Hopefully the lumps will show to be non-cancerous, the only way we'll know for sure is waiting for the pathology report.    

[gayhumv]

Just some FYI.  I had a radical mastectomy in Dec. 1996 and was on tamoxofin for the length prescribed.  In July 2001 I had a large tumor removed above the area where my breast was removed.  My Oncologist said that the tamoxofin was a hinderance on removing that tumor.  I have now had my third and fourth tumor removed on my left side.  I'm not so sure tamoxofin is the right answer for anyone.