In an effort to examine whether RT lowers the risk of mastectomy outside of clinical trial settings, Jeffrey M. Albert, M.D., from the University of Texas MD Anderson Cancer Center in Houston, and colleagues identified 7,403 women (aged 70 to 79 years) with stage 1, estrogen receptor-positive breast cancer who underwent CS between 1992 and 2002. Data obtained from the linked Surveillance, Epidemiology, and End Results-Medicare database were used to determine if patients underwent radiation therapy and to identify women who underwent mastectomy subsequent to initial treatment.

The researchers found that, over a median 7.3 years of follow-up, the risk of subsequent mastectomy within 10 years of diagnosis was 3.2 and 6.3 percent for those who did and did not receive RT, respectively (P < 0.001). RT correlated with a significantly reduced risk of mastectomy (hazard ratio, 0.33). RT was associated with an absolute reduction in risk of mastectomy that ranged from 4.3 to 9.8 percent at 10 years for all subgroups, with the exception of patients aged 75 to 79 years without high-grade tumors who had a pathologic lymph node assessment (P = 0.80).

"Outside of a clinical trial, the receipt of RT after CS was associated with a greater likelihood of ultimate breast preservation for most older women with early breast cancer," the authors write.

The study was funded in part by Varian Medical Systems.

Abstract
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