External Beam Accelerated Partial-Breast Irradiation Using 32 Gy in 8 Twice-Daily Fractions: 5-Year Results of a Prospective Study

Abstract

PURPOSE External-beam accelerated partial breast irradiation (APBI) is an increasingly popular technique following treatment of patients for early-stage breast cancer with conventional breast-conserving therapy. Here we present 5-year results of a prospective trial. METHODS AND MATERIALS From 10/2003 through 11/2005, 98 evaluable patients with Stage I breast cancer were enrolled on the first dose-step (32 Gy delivered in 8 twice-daily fractions) of a prospective, multi-institutional, dose-escalation clinical trial of three-dimensional conformal external-beam APBI (3D-APBI). The median age was 61 years; the median tumor size was 0.8 cm; 89% of tumors were estrogen receptor positive; 10% had a triple-negative phenotype; and 1% had a HER-2-positive subtype. Median follow-up was 71 months (range, 2–88 months; interquartile range 64–75 months). RESULTS Five patients developed IBTR, for a 5-year actuarial IBTR rate of 5% (95% confidence interval, 1–10%). Three of these occurred in patients with triple-negative disease and 2 in non-triple-negative patients, for 5-year actuarial IBTR rates of 33% (0–57%) and 2% (0–6%; p<0.0001), respectively. On multivariate analysis, triple-negative phenotype was the only predictor of IBTR, with borderline statistical significance after adjusting for tumor grade (p=0.0537). CONCLUSIONS Overall outcomes were excellent, particularly for patients with estrogen receptor positive disease. Patients in this study with triple-negative breast cancer had a significantly higher IBTR rate than patients with other receptor phenotypes when treated with 3D-APBI. Larger, prospective 3D-APBI clinical trials should continue evaluating the effect of hormone receptor phenotype on IBTR rates.

Accelerated Partial Breast Irradiation: Executive summary for the update of an ASTRO Evidence-Based Consensus Statement

“…8 In the Massachusetts General Hospital phase 2 trial of 3-dimensional (3D) conformal radiation therapy (3D-CRT) APBI, an IBTR occurred in 2 of 15 women aged 40 to 49 (14% actuarial risk) compared with 3 of 83 in those age ≥50 years (3% actuarial risk), with median follow-up 71 months, although this difference was not statistically significant. 9 The 2 patients less than 50 years of age who had an IBTR both had triple negative disease.…”

“…29,36,37 However, other clinical series of APBI delivered with 3D-CRT or IMRT reported acceptable cosmetic outcomes. 9,[38][39][40][41][42][43][44][45] These conflicting studies raise the hypothesis that subtle variations in planning techniques and/or dose constraints may substantially modify the therapeutic ratio of EBRT-based APBI. [46][47][48] In light of ongoing research, particularly the National Surgical Adjuvant Breast and Bowel Project B-39/RTOG 0413 trial, 5 which has yet to report cosmetic outcomes for patients treated with 3D-CRT APBI, the task force opted not to make a specific recommendation either for or against the use of EBRT-based APBI at this time.…”

Long-Term Update of NRG Oncology RTOG 0319: A Phase 1 and 2 Trial to Evaluate 3-Dimensional Conformal Radiation Therapy Confined to the Region of the Lumpectomy Cavity for Stage I and II Breast Carcinoma

“…These trials vary widely in length of follow-up and sample size. The TARGIT 9 , American Society of Breast Surgeons (ASBS) 10 , NYU 11 , ELIOT 12 , Boston-3D-CRT 13 , Hungary 6 , Boston-Interstitial 7 and RTOG 95-17 8 trials have follow-up of ranging from 2.4-12 years with sample sizes ranging from 50-1721 treated patients. Cumulative incidences of ipsilateral breast recurrence range widely, primarily associated with length of follow-up.…”

Trends and controversies in multidisciplinary care of the patient with breast cancer

“…In addition, the most appropriate patients for APBI, and the optimal technique, will need to be clarified with additional study. Preliminary studies have prompted caution in patients with triple negative disease (91), and those with an extensive intraductal component and lymphvascular space invasion (92). At the present time, the ASTRO consensus panel (93) recommends confining APBI to patients older than 60, with T1N0, ER+ invasive ductal carcinoma and no lymphvascular space invasion, unless patients are participating in a trial.…”