We have previously discussed this question about timing from breast surgery to chemotherapy, with the pat answer that around 2 months or less is safest, and after three months one starts to lose some of the benefit of chemotherapy in terms of increasing cure rate.

A similar question can be asked about radiation therapy for women who have had a lumpectomy, or who have reasons to have radiation after a mastectomy (large tumor, multiple positive lymph nodes e.g.). A study of SEER data looking at women with early stage breast cancer provides an answer. This analysis by Dr. Gold et al concludes that a delay in starting radiation therapy of 12 or more weeks after surgery of 8 or more weeks after chemotherapy was associated with a much higher rate of a local recurrence/relapse.