January 15, 2009 - There is no survival disadvantage to waiting up to 20 weeks to start radiation therapy (RT) after breast-conserving surgery (BCS), but delaying more than that does adversely affect outcomes, according to results from a large study published in the January 2009 issue of Journal of Clinical Oncology (J Clin Oncol, 2009 Jan 1, IA Olivotto, et al).
"To date, the optimal, maximally acceptable delay time to begin RT after BCS has not been clearly defined," noted Lee Schwartzberg, M.D., Ph.D., editor-in-chief of OncologySTAT.
Dr. Schwartzberg noted that "[t]his prospectively evaluated, large, population-based study from British Columbia determined that initiation of external-beam RT up to 20 weeks after BCS, in the absence of adjuvant chemotherapy, was associated with similar outcome to earlier initiation. Delay beyond 5 months significantly compromised both the local-regional failure rate (10 percent vs 5.6 percent) and breast cancer–specific survival.
He added, "Left unanswered is how the interspersion of adjuvant systemic chemotherapy, typically given after BCS and before RT, would affect these results."
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April 10, 2026 
