Breast-Conserving Surgery Followed by Partial or Whole Breast Irradiation: Twenty-Year Results of a Phase 3 Clinical Study.

PURPOSE: To report the 20-year results of a phase 3 clinical trial comparing the survival and cosmetic results of breast-conserving surgery followed by partial breast irradiation (PBI) or whole breast irradiation (WBI).

METHODS AND MATERIALS: Between 1998 and 2004, 258 selected patients with low-risk invasive breast carcinoma (pT1 pN0-1mi, grade 1-2, nonlobular breast cancer) resected with negative margins were randomized after breast-conserving surgery to receive PBI (n = 128) or 50 Gy WBI (n = 130). Partial breast irradiation was given either by multicatheter high-dose-rate (HDR) brachytherapy (BT; n = 88) with 7 × 5.2 Gy twice daily or 50 Gy external beam irradiation with electron beams (n = 40).

RESULTS: Median follow-up time was 17 years. The 20-year actuarial rates of ipsilateral breast tumor recurrences were 9.6% versus 7.9% (P = .59) in the PBI and WBI arms, respectively. There was no significant difference in the 20-year probability of disease-free (79.7% vs 78.3%), cancer-specific (92.6% vs 88.1%), and overall survival (59.5% vs 59.7%). Significantly more patients had excellent or good cosmetic result in the PBI and WBI groups (79.2% vs 59.5%; P = .0007).

CONCLUSIONS: The 20-year updated results of our phase 3 clinical trial add further scientific evidence that PBI either with multicatheter HDR BT or electron beams for low-risk invasive breast carcinomas yield long-term local tumor control and survival comparable to those achieved with standard WBI. Interstitial HDR BT improved cosmetic results compared with WBI.