Trends in hypofractionated radiotherapy use among patients with breast or prostate cancer: a multicenter study in Osaka, Japan.

The uptake of hypofractionated radiotherapy in Japan is not well documented. This study examined trends in the proportion of patients with breast or prostate cancer who received hypofractionated radiotherapy, using hospital-based cancer registry data linked to Diagnostic Procedure Combination records from 69 institutions in Osaka Prefecture (diagnosis years: 2019-23). Eligible patients included 6475 women with unilateral breast cancer (pTisN0M0, pT1-2N0M0 or cT1-2N0M0 before neoadjuvant therapy) who underwent partial mastectomy and radiotherapy at the same hospital and 3274 men with cT1-3N0M0 prostate cancer treated with external-beam radiotherapy without surgery or brachytherapy. The use of hypofractionated radiotherapy was determined through insurance claims. Among the patients with breast cancer, the proportion of those who received hypofractionated radiotherapy increased from 41% in 2019 to 81% in 2023. In 2023, this proportion was highest at facilities with high radiotherapy volume (95%), followed by those with medium (84%) and low (67%) volumes. Among the patients with prostate cancer, the proportion of those who received hypofractionated radiotherapy (hypofractionated intensity-modulated radiotherapy or stereotactic body radiotherapy) increased from 25% in 2019 to 48% in 2023, although the increase slowed after 2021. In 2023, hypofractionated radiotherapy use reached 79% at high-volume facilities, while proportions were lower at medium- (30%) and low-volume (17%) facilities. Hypofractionated radiotherapy use has increased in patients with breast and prostate cancers. However, its adoption in prostate cancer treatment remains limited, particularly in medium- and low-volume facilities. These findings suggest that certain barriers limit its implementation and highlight the need to address them.