Robotic Stereotactic Boost in Early Breast Cancer, a Phase 2 Trial

Abstract

To evaluate the feasibility and toxicity of a single-fraction 8-Gy stereotactic boost after whole-breast irradiation in early breast cancer. The primary aim of this phase 2 study was to evaluate cutaneous breast toxicity using National Cancer Institute Common Terminology Criteria for Adverse Events (version 4) 3months after the boost. Secondary objectives were local control, survival, and patient-reported quality of life using the European Organisation for Research and Treatment of Cancer QLQ-C30 and breast-specific European Organisation for Research and Treatment of Cancer QLQ-BR 23 questionnaires. Patients with invasive ductal or lobular pT1-2 breast cancer treated with lumpectomy with clear margins and pN0 were included. Patients requiring chemotherapy were excluded. Twenty-eight eligible patients received the planned boost, and 26 had hormonal therapy. The procedure was technically successful without procedural complications. A median of 3 fiducials were tracked, and 115 beams were used. There were 22 acute grade 1 breast skin toxicities, including fibrosis, pain, erythema, or pigmentation. There were 2 acute grade 2 erythemas. Median skin boost dose was inversely correlated with acute skin toxicity (P=.028). QLQ-C30 scores revealed acute dyspnea and arm symptoms without correlation to the boost dose. Breast symptom QLQ-BR23 scores did not deteriorate, although upset with hair loss and systemic side effects of hormonal therapy were observed. After a median follow-up of 38months, 1 patient had in-boost-field relapse, and there were 5 late grade 1 and 1 grade 2 skin toxicities. Single-fraction stereotactic boost after conventional whole-breast irradiation in early breast cancer is feasible with minor toxicities. Quality of life and specific breast items showed excellent patient acceptance.