Increase in Hypofractionated Radiotherapy among Patients with Invasive Breast Cancer or Ductal Carcinoma In Situ: Who is Left Behind?

Purpose We aimed to update the trend of hypofractionated whole-breast irradiation (HF-WBI) use over time in the US and examine factors associated with lack of HF-WBI adoption for patients with early-stage invasive breast cancer (IBC) or ductal carcinoma in situ (DCIS) undergoing a lumpectomy. Methods and Materials Among patients who underwent a lumpectomy, we identified 928,034 early-stage IBC patients and 330,964 DCIS patients in the 2004-2020 National Cancer Database. We defined HF-WBI as 2.5–3.33 Gy/fraction to the breast and conventional fractionated whole-breast irradiation as 1.8–2.0 Gy/fraction. We evaluated the trend of HF-WBI utilization using a generalized linear model with the log link and binomial distribution. Factors associated with HF-WBI utilization were assessed using multivariable logistic regression in patients diagnosed between 2018 and 2020. Results Among IBC patients, HF-WBI use has significantly increased from 0.7% in 2004 to 63.9% in 2020. Similarly, HF-WBI usage among DCIS patients has also increased significantly from 0.4% in 2004 to 56.6% in 2020. Black IBC patients were less likely than White patients to receive HF-WBI (adjusted odds ratio [AOR] 0.81, 95% CI: 0.77-0.85). Community cancer programs were less likely to administer HF-WBI to IBC patients (AOR 0.80, 95% CI: 0.77-0.84) and to those with DCIS (AOR 0.87, 95% CI: 0.79-0.96) than academic/research programs. Younger age, positive nodes, larger tumor size, low volume programs, and facility location were also associated with lack of HF-WBI adoption in both patient cohorts. Conclusions HF-WBI utilization among post-lumpectomy patients has significantly increased from 2004-2020 and can finally be considered standard of care in the US. We found substantial disparities in adoption within patient and facility subgroups. Reducing disparities in HF-WBI adoption has the potential to further alleviate healthcare costs while improving patients’ quality of life.