Abstract P4-12-14: Has hypofractionated whole breast radiation therapy become standard of care in the United States? An updated report from national cancer database

Background: Although overwhelming results of randomized controlled trials have demonstrated that hypofractionated whole breast radiation therapy (HF-WBI) has similar recurrence rates and disease-free survival as compared to conventional fractionated whole breast radiation (CF-WBI), we and others have shown that the adoption of HF-WBI remained low in the United States by 2013. It is unknown whether the utilization of HF-WBI has changed after 2013 in the United States. Methods: Among the patients who underwent a lumpectomy, we identified 688,079 patients with early stage invasive breast cancer and 248,218 patients with ductal carcinoma in situ (DCIS) in the National Cancer Database from 2004-2016. We defined HF-WBI as 2.5-3.33 Gy/fraction to the breast, while CF-WBI as 1.8-2.0 Gy/fraction. We evaluated the trend of HF-WBI utilization and examined factors associated with HF-WBI utilization using logistic regression models. Results: Among invasive cancer patients, the usage of HF-WBI increased significantly from 0.7% in 2004 to 15.6% in 2013 and then to 38.1% in 2016. Among DCIS patients, the usage of HF-WBI has increased significantly from 0.4% in 2004 to 13.4% in 2013 and then to 34.3% in 2016. The upsurge of HF-WBI therapy did not affect the overall use of radiotherapy as there was a corresponding decrease in CF-WBI use over these years. In the analysis of factors related to HF-WBI among invasive breast cancer patients, we found that age is strongly correlated with HF-WBI utilization and it is more likely for older patients to receive HF-WBI than younger patients. The proportion of HF-WBI use was 9.3% among women younger than age 50 while 21.8% of women older than 50 years were treated with HF-WBI. Another factor found was race/ethnicity; we found that among African American women with invasive breast cancer, 12.7% used HF-WBI and among Asian women with invasive breast cancer, 23.6% used HF-WBI, while 15.6% of white women used HF-WBI. Among the invasive breast cancer patients, HF-WBI use varied widely across geographical location with the highest uptake in the Mountain census region (25.3%) and least uptake in the West South Central region (10.5%). Other factors associated with HF-WBI use for invasive breast cancer patients included nodal status, tumor size, treating facility type, treating facility volume, and distance from home to treating facility. We found that large academic facilities were more likely to administer HF-WBI (24.4%) than small community treating facilities (11.2%). Our results for DCIS patients were similar to that of the invasive breast cancer patients. Conclusions: HF-WBI utilization in the United States has more than doubled from 2013 to 2016. Although its use is close to that of conventional WBI, HF-WBI is still far from preferred standard of care in the United States. We identified several patient and facility factors that can impact the uptake of HF-WBI treatment. Citation Format: Dezheng Huo, Minji Kang, Loren Saulsberry, Yasmin Hasan. Has hypofractionated whole breast radiation therapy become standard of care in the United States? An updated report from national cancer database [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-14.