A Clinical Study of Radical APBI Using Carbon-Iron Irradiation for Patients With Stage I Breast Cancer

Abstract

Purpose/Objective(s): Our institute initiated a clinical study of radical accelerated partial breast irradiation (APBI) for stage I breast cancer using carbon-ion radiation therapy (C-ion RT). The purpose of this report is to evaluate preliminary treatment results. Materials/Methods: Candidates for clinical trial are patients with low-risk stage I breast cancer who are suitable for APBI in ASTRO consensus statement (2009). Tumors located more than 5 mm from the skin and no prior treatment are also eligibility criteria. A dose escalation study was designed as a phase I clinical trial with the dose level based on our experience. Total dose is 48.0 GyE, 52.8 GyE, and 60.0 GyE in 4 fractions within one week, at fraction sizes of 12 GyE, 13.2 GyE, and 15 GyE, respectively. In phase I, patients plan to undergo surgery for pathological evaluation 90 days after C-ion RT and then receive endocrine therapy. In phase II, patients have C-ion RT at recommended dose and then receive endocrine therapy. Treatment posture is supine, with an immobilization cast, fixation body and breast shells. Three-field C-ion beams with 290 MeV/n energy is used by means of passive broad beam methods using individual collimators and a compensation bolus absorber. Irradiation is performed using respiratory gating. Primary end points are early normal tissue reaction and tumor control at recommended dose. Secondary end points are CR rate, late normal tissue reaction, cosmetic outcome, diseasefree survival, and overall survival. Patients with stage I breast cancer desiring to receive C-ion RT but ineligible to enroll in the clinical trial due to variance or refusal to enroll in the clinical trial, although certain reasons make them unsuitable for standard treatment, were treated by “C-ion RT general treatment protocol for localized solid tumors” with the patient’s and institute’s agreement. The first 2 patients of this “general protocol” were treated by 52.8 GyE and the others by 60 GyE. The patients were suitable for endocrine therapy after RT. Results: From April 2013 to February 2015, 3 cases of 48 GyE, 3 cases of 52.8 GyE and 1 case of 60 GyE of phase I were treated, and 2 cases of 52.8 GyE and 5 cases of 60 GyE of “general protocol” were treated. Patients’ age ranged from 44 to 81 years, median 66 years. Tumor size was 4 to 20 mm, median 12 mm. The follow-up period ranged from 1 to 22 months, median 9 months. No adverse reactions in normal tissue were observed except for grade 1 skin reaction of CTC-AE v4 in 5 cases. At the time of analysis, 6 patients underwent surgery and 2 of them reached pathological CR. Of the “general protocol” patients, 4 reached CR, 2 reached PR, and 1 developed PD on MRI. The PD patient with triple negative subtype tumor was successfully salvaged by surgery. Conclusion: C-ion RT for patients with stage I breast cancer seems useful, and the significance of continuing the study is recognized. Author Disclosure: K. Karasawa: None. T. Omatsu: None. S. Fukuda: None. T. Kamada: None. N. Yamamoto: None. T. Ishikawa: None. A. Arakawa: None. M. Saito: None.