Disease Control After Hypofractionation Versus Conventional Fractionation for Triple Negative Breast Cancer: Comparative Effectiveness in a Large Observational Cohort.

PURPOSE: Questions remain about whether moderately hypofractionated whole-breast irradiation is appropriate for patients with triple-negative breast cancer. METHODS AND MATERIALS: Using the prospective database of a multicenter, collaborative quality improvement consortium, we identified patients with node-negative, triple-negative breast cancer who received whole-breast irradiation with either moderate hypofractionation or conventional fractionation. Using inverse probability of treatment weighting (IPTW), we compared outcomes using the Kaplan-Meier product-limit estimation method with Cox regression models estimating the hazard ratio for time-to-event endpoints between groups. RESULTS: The sample included 538 patients treated at 18 centers in 1 state in the United States, of whom 307 received conventionally fractionated whole-breast irradiation and 231 received moderately hypofractionated whole-breast irradiation. The median follow-up time was 5.0 years (95% confidence interval [CI], 4.77-5.15 years). The 5-year IPTW estimates for freedom from local recurrence were 93.6% (95% CI, 87.8%-96.7%) in the moderate hypofractionation group and 94.4% (95% CI, 90.3%-96.8%) in the conventional fractionation group. The hazard ratio was 1.05 (95% CI, 0.51-2.17; P = .89). The 5-year IPTW estimates for recurrence-free survival were 87.8% (95% CI, 81.0%-92.4%) in the moderate hypofractionation group and 88.4% (95% CI 83.2%-92.1%) in the conventional fractionation group. The hazard ratio was 1.02 (95% CI, 0.62-1.67; P = .95). The 5-year IPTW estimates for overall survival were 96.6% (95% CI, 92.0%-98.5%) in the moderate hypofractionation group and 93.4% (95% CI, 88.7%-96.1%) in the conventional fractionation group. The hazard ratio was 0.65 (95% CI, 0.30-1.42; P = .28). CONCLUSIONS: Analysis of outcomes in this large observational cohort of patients with triple-negative, node-negative breast cancer treated with whole-breast irradiation revealed no differences by dose fractionation. This adds evidence to support the use of moderate hypofractionation in patients with triple-negative disease.

Multi-institutional registry study evaluating the feasibility and toxicity of accelerated partial breast irradiation using noninvasive image-guided breast brachytherapy.

PURPOSE: The noninvasive image-guided breast brachytherapy (NIBB) technique is a novel noninvasive yet targeted method for accelerated partial breast irradiation. We established a multi-institutional registry to evaluate the toxicity and efficacy of this technique across various practice settings. METHODS AND MATERIALS: Institutions using the NIBB technique were invited to participate. Data for acute/late toxicity, cosmetic outcome, and tumor recurrence were collected. Toxicity and cosmetic outcome were graded based on the Common Terminology Criteria for Adverse Events version 3.0 and NRG/Radiation Therapy Oncology Group scale, respectively. Treatment variables were analyzed for association with outcomes. RESULTS: A total of 252 patients from eight institutions were analyzed. The median age was 69 years. The mean tumor size was 1.1 cm (0.1-4.0 cm). Treatment was delivered 10 fractions (34-36 Gy) in 75% and five fractions (28.5 Gy) in 22%. B.i.d. fractionation was used in 9%. Acute radiation dermatitis was Grade 0-1, 2, and 3 in 77%, 19%, and 4%, respectively. One hundred ninety-one patients with a median followup of 18 months (4-72 months) were evaluable for late outcomes. Late toxicity Grades 2 and 3 were observed in 8.8% and 1%, respectively. Cosmetic outcome was excellent, good, and fair/poor in 62%, 36%, and 2%, respectively. B.i.d. fractionation was associated with higher acute and late toxicity. Second-generation applicators were associated with lower late toxicity and better cosmetic outcome. Actuarial freedom from ipsilateral breast tumor recurrence and true recurrence were 98.3% and 98.3% at 2 years and 90.9% and 95.4% at 5 years, respectively. CONCLUSIONS: Accelerated partial breast irradiation using NIBB was well tolerated with a low rate of acute and late toxicity across various practice settings. Ipsilateral breast tumor recurrence and cosmetic outcomes were favorable. b.i.d. fractionation was associated with higher toxicity. Longer followup is needed to confirm late endpoints.

The Role of Facility Variation on Racial Disparities in Use of Hypofractionated Whole Breast Radiation Therapy.

PURPOSE: Hypofractionated radiation therapy is a less burdensome and less costly approach that is efficacious for most patients with early-stage breast cancer. Concerns about racial disparities in adoption of medical advances motivate investigation of the use of hypofractionated radiation in diverse populations. The goal of our study was to determine whether hypofractionated whole breast radiation therapy after breast-conserving surgery was being similarly used across racial groups in the state of Michigan. METHODS AND MATERIALS: A prospectively collected statewide quality consortium database from 25 institutions was queried for patients with breast cancer who completed hypofractionated (HF) or conventionally fractionated whole breast radiation therapy from January 2012 to December 2018. We used patient-level multivariable modeling to evaluate associations between HF use and race, controlling for patient and facility factors, and multilevel modeling to account for patient clustering within facilities. RESULTS: Of 9634 patients analyzed, 81% self-reported race as white, 17% as black, and 2% as Asian, similar to statewide and national distributions. In addition, 31.7% of whites were treated at teaching centers compared with 66.7% of blacks and 64.8% of Asians. In 2018, HF was used in 72.7% of whites versus 56.7% of blacks and 67.6% of Asians (P = .0411). On patient-level multivariable analysis, black and Asian races were significantly associated with a lower likelihood of HF receipt (P < .001), despite accounting for treatment year, age, laterality, body mass index, breast volume, comorbidities, stage, triple-negative status, intensity modulated radiation therapy use, teaching center treatment, and 2011 American Society for Radiation Oncology Hypofractionation Guideline eligibility. On multilevel analysis, race was no longer significantly associated with HF receipt. CONCLUSIONS: We observed that black and Asian patients receive hypofractionated whole breast radiation therapy less often than whites, despite more frequent treatment at teaching centers. Multilevel modeling eliminated this disparity, suggesting that differences in facility-specific HF use appear to have contributed. Further inquiry is needed to determine whether reduction of facility-level variation may reduce disparities in accessing HF treatment.