Phase 2 Trial of Ultrahypofractionated Image-guided Partial Breast Irradiation Following Lumpectomy with Optional Oncoplastic Reconstruction for Early-stage Breast Cancer

Abstract

Purpose: As accelerated partial breast irradiation is gaining widespread acceptance for low-risk breast cancers treated with breast conservation, its role following oncoplastic surgery remains controversial.

Methods and materials: We performed a prospective phase 2 trial of women aged 50 and older who were estrogen receptor positive with stage 0 to 1 breast cancer measuring ≤3 cm following successful lumpectomy with optional oncoplastic reconstruction. Patients were treated on the Varian Edge radiosurgery system to a prescribed dose of 30 Gy in 5 fractions, and the primary endpoints were feasibility and safety. Patient-reported cosmesis was assessed using the Breast Cancer Treatment Outcome Scale validated instrument.

Results: From 2018 to 2022, 50 patients with 52 tumors with a median age of 76 were enrolled, including 79% invasive breast cancer with 48% undergoing oncoplastic reconstruction. With a median follow-up of 47 months, long-term patient-reported cosmesis was excellent in 89% of patients and good in 11% of patients. All patients were locally controlled, but there were 2 ipsilateral breast events consisting of an intramammary lymph node failure and second primary triple-negative breast cancer outside the radiation field, both successfully salvaged with further local and systemic therapy.

Conclusions: In carefully selected patients with low-risk early-stage breast cancer, patients treated with a 5-fraction regimen of partial breast irradiation achieve excellent cosmetic and oncological outcomes. Oncoplastic reconstruction was not a contraindication to partial breast irradiation.

Figure 1

Percentage of 52 patients at each of the 4 cosmesis scores at baseline (blue) and greater than 2-year follow-up (red). Abbreviation: BCTOS = Breast Cancer Treatment Outcome Scale.

Figure 2

Radiation, MRI, and photographic imaging eliciting oncoplastic reconstruction. (A) Radiation dose distribution in a patient treated with lumpectomy with oncoplastic reconstruction. The tumor bed is contoured in red, the PTV30 in cyan, and the PTV28.5 in dark blue. (B) Bilateral breast MRI with contrast demonstrates subareolar enhancing mass to assist with target delineation despite oncoplastic reconstruction. (C) Photographic example of an excellent physician- and patient-reported cosmetic outcome despite a large right breast PTV30 volume of 397 cc. Abbreviations: MRI = magnetic resonance imaging; PTV = planned tumor volume.

Figure 3

Kaplan-Meier curve eliciting 4-year oncological outcomes for patients treated with partial breast irradiation. (A) Overall survival (90%), (B) regional recurrence-free survival (98.%), (C) disease-free survival (88%), (D) local control (100%), (E) distant control (100%).