TIME FRAME FOR CHEMO

Is there a time frame after surgery for Breast CA that adjuvant chemo must be given or it loses it's value...I've heard 1 month, 6 weeks and 8 weeks. Is it true that the benefit is gone if one waits longer than 8 weeks.
Thanks

[CCF-RN,MSN-JS]

Dear medicall, The purpose of adjuvant treatment is to treat any microscopic cancer that may have spread.  There is no magic number for when adjuvant chemotherapy should start, however in most clinical trials for adjuvant therapy the requirement is that treatment start within 6 weeks of surgery.  
Outcomes reported on the effectiveness of adjuvant therapy are based on this timeframe.