Tumor bed boost omission after negative re-excision in breast-conservation treatment.

BACKGROUND: We evaluated the necessity of a tumor bed boost after whole-breast radiotherapy for early-stage breast cancer after breast-conserving surgery and negative re-excision.

METHODS: Of patients treated at the Virginia Commonwealth and Tufts Universities with breast-conservation therapy for early-stage breast cancer between 1983 and 1999, 205 required re-excision of the tumor cavity to obtain clear margins and were found to be without residual disease. Adjuvant conventionally fractionated whole-breast radiotherapy was given to a total dose of 50 Gy in 25 fractions. The tumor bed boost was omitted.

RESULTS: The median follow-up was 98 months (range, 6-229 months). The tumor histological diagnosis was primarily infiltrating ductal carcinoma (183 cases; 89%). Nodal involvement was documented in 49 cases (24%). There were four documented recurrences at the tumor bed site. Five in-breast recurrences were documented to be in a location removed from the tumor bed. The overall Kaplan-Meier 15-year in-breast control rate was 92.4%, and the freedom from true recurrence rate was 97.6%.

CONCLUSIONS: The findings support the concept that postlumpectomy radiotherapy can be tailored according to the degree of surgical resection. There is an easily identifiable subgroup of patients who can avoid a tumor bed boost, thus resulting in a reduced treatment time and improved cosmesis, while maintaining local control rates that approach 100%. The data suggest that in patients who undergo a negative re-excision, treatment with whole-breast radiotherapy to 50 Gy is a sufficient dose to maximally reduce the risk of local recurrence.