Long-term results from the NRG Oncology clinical trial NSABP B-39/RTOG 0413 comparing whole-breast irradiation (WBI) to accelerated partial-breast irradiation (APBI) indicated that, although the absolute difference between treatment was less than 1%, APBI did not meet the criteria for equivalence to WBI in controlling ipsilateral breast tumor recurrence (IBTR) after breast-conserving therapy. The trial provided the longest follow-up reported to date in the largest and most diverse group of patients treated with APBI; it is also the first study to include all forms of APBI. These results were published in The Lancet.
Trial participants on NSABP B-39/RTOG 0413 were randomly assigned to receive either WBI in 25 daily fractions of 2 Gy (50 Gy over five weeks) +/- a tumor bed boost (to 60 Gy) or APBI in 34 Gy of brachytherapy or 38.5 Gy of external-beam radiotherapy delivered in 10 fractions over 5 treatment days. The goal of the trial was to determine if treatment with APBI could shorten the treatment duration for patients while being equally as effective as WBI treatment.
Between March 2005 and April 2013, the trial enrolled 4,216 women and, of that group, 2,036 patients in the WBI group and 2,089 in the APBI group were available for survival analysis. At the 10-year follow-up, the cumulative incidence of IBTR was 4.6% (95% CI 3.7-5.7) in the APBI treatment group versus 3.9% (3.1-5.0) in the WBI treatment group. Treatment related toxicities and second cancers were similar between treatment groups.
"The value of our trial is that it has a large, diverse population of patients and sufficient power to demonstrate that APBI should not replace WBI in all types of patients who undergo lumpectomy. However, with an absolute difference of less than 1% in the 10-year cumulative incidence of IBTR, APBI might be chosen as an acceptable alternative for some women." said Frank Vicini, MD, principal investigator at the MHP Radiation Oncology Institute/21st Century Oncology in Pontiac, Michigan and Julia White MD, co-principal investigator at The Ohio State University. Dr. White added, "Differences in outcomes among the various forms of APBI, as well as quality of life (including patient-reported outcomes and cosmetic results), and quality assurance analyses will be reported separately"
This study was funded by the NCI, Department of Health and Human Services, Public Health Service Grants U10-CA-180868, U10-CA-180822, and UG1CA-189867.
Vicini FA, Cecchini RS, White JR, Arthur DW, Julian TB, Rabinovitch RA, Kuske RR, Ganz PA, Parda DS, Scheier MF, Winter KA, Paik S, Kuerer HM, Vallow LA, Pierce LJ, Mamounas EP, McCormick B, Costantino JP, Bear HD, Germain I, Gustafson G, Grossheim L, Petersen IA, Hudes RS, Curran Jr. WJ, Bryan JL, Wolmark N. Long-term primary results of accelerated partial breast irradiation after breast-conserving surgery for early-stage breast cancer: A randomized, phase 3, equivalence trial. Lancet. 2019 Dec 5. [Epub ahead of print]
About NRG Oncology
NRG Oncology conducts practice-changing, multi-institutional clinical and translational research to improve the lives of patients with cancer. Founded in 2012, NRG Oncology is a Pennsylvania-based nonprofit corporation that integrates the research of the legacy National Surgical Adjuvant Breast and Bowel Project (NSABP), Radiation Therapy Oncology Group (RTOG), and Gynecologic Oncology Group (GOG) programs. The research network seeks to carry out clinical trials with emphases on gender-specific malignancies, including gynecologic, breast, and prostate cancers, and on localized or locally advanced cancers of all types. NRG Oncology's extensive research organization comprises multidisciplinary investigators, including medical oncologists, radiation oncologists, surgeons, physicists, pathologists, and statisticians, and encompasses more than 1,300 research sites located world-wide with predominance in the United States and Canada. NRG Oncology is supported primarily through grants from the National Cancer Institute (NCI) and is one of five research groups in the NCI's National Clinical Trials Network.