Study details
Dr. Vicini and colleagues enrolled in their trial 4,216 women with stage 0-II breast cancer who had undergone lumpectomy. They were randomized to whole-breast irradiation (5-6 weeks of radiation therapy at that time) or partial-breast irradiation using one of three techniques (3D conformal external beam radiation completed in 5 days, interstitial brachytherapy completed in 5 days, or device-based brachytherapy).
The hazard ratio for ipsilateral breast tumor recurrence (invasive or DCIS) as a first recurrence with partial-breast irradiation versus whole-breast irradiation was 1.22, with the upper bound of the 90% confidence interval (0.94-1.58) falling just outside the predefined range to declare the two modalities equivalent (0.667-1.5), Dr. Vicini reported. However, the absolute difference in the 10-year cumulative incidence of ipsilateral breast tumor recurrences was merely 0.7% (4.6% vs. 3.9%).
The 10-year recurrence-free interval was inferior with partial-breast irradiation (hazard ratio, 1.33; P = .02), but the absolute difference was again small at 1.6% (91.8% vs 93.4%). The partial- and whole-breast irradiation groups were statistically indistinguishable on distant disease-free interval (96.7% vs 97.1%; HR, 1.31; P = .15) and overall survival (90.6% vs. 91.3%; HR, 1.10; P = .35).
Dr. Vicini disclosed that he is a research advisor for ImpediMed. The study was sponsored by the National Cancer Institute.
SOURCE: Vicini FA et al. SABCS 2018, Abstract GS4-04,