For a breast cancer patient treated with a mastectomy who has clear indications for post-mastectomy radiation therapy, what do you consider to be the longest acceptable delay prior to initiating PMRT following surgery?

The longest I've ever waited is 6 months, and that was in a young patient with T4b N3b M0 disease that progressed on weekly taxol and then experienced a complete pathologic response to FAC. I felt that this patient had a substantial risk of local-regional recurrence and that even if the benefit of radiation were to be attenuated, it would not be completely nullified.

I generally consider radiation to lower the risk of local-regional recurrence by approximately 70%, though this likely varies by receptor subtype. As the time from surgery grows, this benefit is likely attenuated. It is difficult to precisely quantitate the degree of attenuation per unit time, and this likely varies by receptor type and adjuvant treatment with hormone therapy o...