Accelerated partial breast irradiation through brachytherapy for ductal carcinoma in situ: factors influencing utilization and risks of second breast tumors.

The purpose of this study was to examine influencing factors and outcomes of accelerated partial breast irradiation through brachytherapy (APBIb) versus whole breast irradiation (WBI) for ductal carcinoma in situ (DCIS). From the Surveillance Epidemiology and End Results program of the US National Cancer Institute, we identified 40,749 women who were diagnosed with first primary DCIS between 2002 and 2011 and treated with breast-conserving surgery and radiotherapy. A multi-level logistic regression analysis was performed to estimate odds ratios of APBIb use. Hazard ratios (HRs) of developing ipsilateral breast tumors (IBTs) and contralateral breast tumors (CBTs) were analyzed in 1962 patients with APBIb and 7203 propensity score-matched patients with WBI, using Cox proportional hazards regression. Overall, 2212 (4.5 %) of 40,749 women (the whole cohort) received APBIb. Factors associated with the increased use of APBIb included older age, non-Hispanic white race/ethnicity, smaller tumor size, hormone receptor positivity, comedo subtypes, and urban residence. During the 46-month follow-up, 74 (0.8 %) and 131 (1.4 %) of 9165 propensity score-matched patients developed IBTs and CBTs, respectively. Compared with WBI, APBIb was associated with a significantly increased risk of IBTs (HR 1.74; 95 % CI 1.06-2.85) but not CBTs (OR 0.91; 95 % CI 0.59-1.41). This population-based study suggests that APBIb use for DCIS was influenced by patient and tumor characteristics as well as urbanization of residence. We observed a moderately increased IBT risk associated with APBIb versus WBI, suggesting that APBIb should be used with caution for DCIS before data from randomized controlled trials with long-term follow-ups are available.