FRIDAY, Dec. 20, 2019 (HealthDay News) — For women with primary ductal carcinoma in situ (DCIS), use of radiotherapy (RT) is associated with increased rates of breast cancer-specific mortality for those women who subsequently develop an invasive second breast cancer (SBC), according to a study published in the November issue of the Journal of the National Comprehensive Cancer Network.

Using the Surveillance, Epidemiology, and End Results database, Puyao C. Li, M.D., from Brigham and Women’s Hospital in Boston, and colleagues identified 3,407 patients who received breast-conserving therapy with or without RT for primary DCIS in 2000 through 2013 and subsequently developed a stage I to III invasive SBC.

The researchers found that even after controlling for cancer stage, prior RT was associated with higher rates of breast cancer-specific mortality (hazard ratio, 1.70; 95 percent confidence interval, 1.18 to 2.45; P = 0.005). The risk trended higher in patients with ipsilateral versus contralateral SBC (hazard ratio, 2.07 versus 1.26; P = 0.16). Patients with ipsilateral SBC were younger and more often lacked estrogen receptor expression compared with patients who developed contralateral SBC.

“These findings may have implications for treatment decision-making in DCIS and after development of SBC, and highlight the value of a careful discussion with patients before treatment,” the authors write.

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