Effect of radiotherapy boost and hypofractionation on outcomes in ductal carcinoma in situ.

BACKGROUND

Boost radiotherapy (RT) improves outcomes for patients with invasive breast cancer, but whether this is applicable to patients with pure ductal carcinoma in situ (DCIS) is unclear. This study examined outcomes from whole breast RT, with or without a boost, and the impact of different dose-fractionation schedules in a population-based cohort of women with pure DCIS treated with breast-conserving surgery (BCS).

METHODS

Data was analyzed for 957 subjects diagnosed between 1985 and 1999. RT use was analyzed over time. Ten-year Kaplan-Meier local control (LC), breast cancer specific survival (BCSS), and overall survival (OS) were compared using the log-rank test. Cox regression modeling of LC was performed.

RESULTS

Median follow-up was 9.3 years. Of the patient cohort 475 (50%) had no RT (NoRT) after BCS, 338 (35%) had RT without a partial breast boost (RTNoB), and 144 (15%) had RT with boost (RT + B). Subjects with risk factors of local recurrence were more likely to receive RT. Subjects receiving adjuvant RT had a trend toward improved LC (15-year LC: NoRT 87%; RTNoB 94%; RT + B 91%; P = .065). Multivariable analysis showed that RT with or without a boost was significantly associated with improved LC (HR, 0.29 and 0.38, respectively, compared with NoRT, P = .025), with no difference associated with a boost or different dose-fractionation schedules.

CONCLUSIONS

Adjuvant RT improves local control in patients with DCIS treated with BCS. Hypofractionation is as effective as standard fractionation schedules. Boost RT was not associated with improved LC compared with whole breast RT alone. Cancer 2011. © 2010 American Cancer Society.