A Phase I Study of Intraoperative Radiotherapy for Early Breast Cancer in Japan

Background The present study was designed to identify the optimal intraoperative radiotherapy (IORT) dose for early breast cancer in Japanese women. Methods A phase I study was designed using a scheme of dose-escalation from 19, 20, and 21 Gy at 90% isodose. The primary endpoint was early toxicity. Secondary endpoints were efficacy for a long period and late toxicity. Inclusion criteria were as follows: (1) tumor size 50 years, (3) surgical margin >1 cm, (4) intraoperative pathologically free margins, (5) written informed consent. Exclusion criteria were (1) contraindication to radiation therapy, (2) extensive intraductal component. Partial resection was performed with at least a 1-cm margin around the tumor. Radiation was delivered directly to the mammary gland employing a MOBETRON device. Toxicity was evaluated with the Common Terminology Criteria for Adverse Events (CTCAE), version 3.0. Results From December 2007 to September 2008, 9 patients were enrolled in the study. The first three patients received a radiation dose of 19 Gy. Within 3 months toxicity in each case was deep connective tissue fibrosis (grade 1: 2/3, grade 2: 1/3). The next three patients received a dose of 20 Gy and had toxicities of deep connective tissue fibrosis (grade 1: 3/3), hematoma (grade 1: 2/3), infection in the musculoskeletal soft tissue (grade 1: 2/3), and soft tissue necrosis (grade 2: 1/3). The final three patients received a dose of 21 Gy and had toxicities of deep connective tissue fibrosis (grade 1: 2/3), hematoma (grade 1: 1/3), infection in the musculoskeletal soft tissue (grade 1: 1/3), and soft tissue necrosis (grade 2: 2/3). Conclusions The IORT treatment was tolerated very well in Japanese women, and we now recommend the dose of 21 Gy.