Five Fraction Accelerated Partial Breast Irradiation Versus Intraoperative Radiation Therapy for Early-Stage Breast Cancer

A single institution review of outcomes in 473 patients with early stage breast cancer treated with low -energy TARGIT intraoperative radiation therapy (IORT) or partial breast irradiation (PBI) was performed. Low -Energy IORT was associated with increased rates of any recurrence as well as locoregional failures. Further follow-up is needed for the PBI cohort with the current data supporting previous studies demonstrating increased rates of recurrence with low -energy IORT. Purpose/Objective(s): Accelerated partial breast irradiation (PBI) delivered in 5 fractions with intensity modulated radiation therapy (IMRT) has been shown to have comparable clinical outcomes to whole breast irradiation with reduced toxicity profiles. In contrast, intraoperative radiation therapy (IORT) offers patients the potential to complete adjuvant radiation therapy in a single treatment. While early data were promising, concerns exist regarding long-term rates of local recurrence after IORT. We present a comparison of 5 fraction PBI versus IORT. Materials/Methods: We performed a retrospective review of 473 patients with early -stage breast cancer treated at a single institution from 2011 to 2021 with 258 receiving PBI and 215 receiving IORT. PBI patients received 30 Gy in 5 fractions delivered with IMRT. IORT patients received 20 Gy in 1 fraction prescribed to the applicator surface at surgery using the low -energy TARGIT technique. Results: Mean age was 71 years old (IQR:67-74) for IORT patients and 67 years old (IQR:62-72) for PBI patients. Median follow up was 5.7 years (IQR:4.2-7.0) for IORT patients and 2.4 years (IQR:1.8-3.3) for PBI patients ( P < .001). Recurrence at any time (locoregional and distant) was seen in 7.9% (n = 17) of patients receiving IORT as compared to 0.8% (n = 2) of patients receiving PBI. IORT was associated with reduced rates of locoregional relapse free survival at 5 years (93.6% vs. 99.4%, P = .05) with no difference in overall survival(92.8% vs. 95.1%, P = .99). Conclusion: Lowenergy TARGIT IORT was associated with higher rates of locoregional recurrence compared to PBI. These outcomes, consistent with other series and current guidelines, suggest a limited role for low -energy IORT as monotherapy.