Breast Cancer

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TU_6_3373 - A Multicenter Single-arm Confirmatory Trial on Hypofractionated Whole-breast Irradiation after Breast-conserving Surgery

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

A Multicenter Single-arm Confirmatory Trial on Hypofractionated Whole-breast Irradiation after Breast-conserving Surgery
Y. Kawaguchi1, M. Nozaki2, Y. Kagami3, T. Shibata4, K. Nakamura4, Y. Ito5, Y. Nishimura6, Y. Saito7, Y. Nagata8, Y. Matsumo9, T. Akimoto10, T. Nishimura11, T. Uno12, K. Tsujino13, M. Kataoka14, T. Kodaira15, K. Shiraishi16, K. Inoue17, F. Isohashi18, and M. Hiraoka19; 1Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan, 2Department of Radiology, Dokkyo Medical University Saitama Medical Center, Saitama, Japan, 3Department of Radiation Oncology, Showa University School of Medicine, Tokyo, Japan, 4JCOG Data Center/Operations Office, National Cancer Center Hospital, Tokyo, Japan, 5Department of Radiation Oncology, National Cancer Center Hospital, Tokyo, Japan, 6Department of Radiation Oncology, Kindai University Faculty of Medicine, Osaka, Japan, 7Division of Radiation Oncology, Saitama Cancer Center, Saitama, Japan, 8Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan, 9Department of Radiation Oncology, Niigata Cancer Center Hospital, Niigata, Japan, 10Division of Radiation Oncology and Particle Therapy, National Cancer Center Hospital East, Kashiwa, Japan, 11Radiation and Proton Therapy Center, Shizuoka Cancer Center, Shizuoka, Japan, 12Department of Radiology, Chiba University Hospital, Chiba, Japan, 13Department of Radiation Oncology, Hyogo Cancer Center, Hyogo, Japan, 14Department of Radiotherapy, National Hospital Organization Shikoku Cancer Center, Ehime, Japan, 15Department of Radiation Oncology, Aichi Cancer Center Hospital, Nagoya Aichi 464-8681, Japan, 16Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan, 17Division of Radiotherapy, Tochigi Cancer Center, Tochigi, Japan, 18Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan, 19Japanese Red Cross Wakayama Medical Center, Wakayama, Japan

Purpose/Objective(s): To evaluate the safety and efficacy of hypofractionated whole-breast irradiation (HF-WBI) on Japanese women after breast-conserving surgery (BCS). Primary result of this study (JCOG0906, UMIN000003200) was reported previously, and this is the updated report with 5-year follow-up.

Materials/Methods: Japanese women who had invasive breast cancer with clinical tumor size of <=3 cm, pathologically N0 or N1a and negative inked margin were enrolled. HF-WBI of 42.56 Gy / 16 fractions (fr) was delivered to the whole-breast, and boost irradiation (BI) of 10.64 Gy / 4 fr was added when the surgical margin was <=5 mm. Treatment course should be completed within 29 days (HF-WBI) or 33 days (plus BI). The primary endpoint was the proportion of grade 2 or higher late adverse reactions (ARs) of pre-specified eight items including telangiectasia, ulceration, fibrosis -deep connective tissue, fracture, pneumonitis, cardiac ischemia/infarction, pericardial effusion and pain-breast, occurring between 91 days and 3 years from the start of HF-WBI. The sample size was set as 310 patients (pts) with a one-sided alpha of 5%, power of 90%, threshold value of 8%, and expected value of 4%, estimated from our pilot survey on conventional fractionated (CF)-WBI. Secondary endpoints included the early adverse events (AEs) occurring during 90 days from the start of HF-WBI, overall survival (OS), disease-free survival (DFS), ipsilateral-breast relapse-free survival (IB-RFS), late ARs, and cosmetic outcome. Toxicities were evaluated using CTCAE ver3.0. Cosmetic outcomes were assessed by use of the 4-point scoring system and CTCAE ver3.0.

Results: Between February 2010 and August 2012, 312 pts (I/IIA/IIB; 228/68/16) were enrolled. A total of 306 pts including 66 pts with BI received HF-WBI, but 6 chose CF-WBI prior to the start of irradiation. At the last follow-up in September 2017, median follow-up was 70.5 (7.6–88.9) months. The proportion of grade 2 or higher pre-specified late ARs within 3 years was 4.3% (95% CI 2.3–7.2). The recommended schedule was completed in 301 pts (96.5%; 95% CI 93.8–98.2). Grade 2 early AEs were found in 38 pts (12.4%), and none had grade 3/4. Five-years OS, DFS and IB-RFS were 98.7% (95% CI 96.5-99.5), 95.4% (95% CI 92.3–97.2) and 98.0% (95%CI 95.6–99.1). Among evaluable 304 pts, 29 pts (9.5%; 95% CI 6.5–13.4) had grade 2/3 late ARs. None had grade 4 or treatment-related death. At 5 years, 232 pts (75.8%) had a good or excellent cosmetic outcome, while 70 (24.2%; 95% CI 19.4–29.6) of 289 pts, who were assessed on the breast appearance including hyper/hypopigmentation, breast nipple/areolar deformity, breast volume and deformity, showed any poorer appearance than that at the registration.

Conclusion: HF-WBI is considered to be one of the standard treatments for Japanese women with margin-negative invasive breast cancer after BCS.

Author Disclosure: Y. Kawaguchi: None. M. Nozaki: None. T. Shibata: None. K. Nakamura: None. Y. Ito: None. Y. Saito: None.

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