Impact of COVID-19 Pandemic on Carbon-Ion Radiation Therapy in Japan: A Japanese National Registry Study.

Purpose: This study aimed to investigate the impact of the COVID-19 pandemic on carbon-ion radiation therapy (CIRT) in Japan by evaluating patient numbers and treatment trends from 2019 to 2022. Patients and Methods: Data from 5 CIRT facilities were analyzed, encompassing a total of 13 224 patients treated over the 4-year period. Patient demographics, cancer types, treatment protocols, and adherence to national health insurance coverage were examined. The study period was divided into unaffected (2019), significantly affected (2020-2021), and poststabilization (2022) phases, corresponding to progression of the pandemic. For monthly analysis, the period during which a state of emergency was declared by the Japanese government was defined as the pandemic period. Results: Prostate cancer comprised the majority of CIRT cases (62.4%), followed by hepatocellular carcinoma, bone and soft tissue tumors, locally advanced pancreatic cancer, and nonsquamous cell carcinoma of the head and neck. Despite the pandemic, the annual reduction in CIRT patients remained <5%, suggesting treatment continuity. Analysis of monthly treatment figures revealed a significant reduction in the number of patients with nonprostate cancers treated during the state of emergency, while a reduction in the number of prostate cancer treatments was observed approximately 6 months later. Although the number of COVID-19 patients continued to increase after 2022, the number of patients receiving CIRT increased after the state of emergency was declared. Conclusion: Although there was a reduction in monthly CIRT patient numbers during the COVID-19 pandemic, yearly analysis revealed that this amounted to <5%.