METHODS: We conducted a population-based study using data from the Global Cancer Observatory (GLOBOCAN) 2022 and predicted global radiotherapy demands and workforce requirements in 2050. We obtained incidence figures for 29 types of cancer across 183 countries and derived the cancer-specific radiotherapy use rate using the 2013 Collaboration for Cancer Outcomes Research and Evaluation model. We delineated the proportion of people with cancer who require radiotherapy and can be accommodated within the existing installed capacity, assuming an optimal use rate of 50% or 64%, in both 2022 and 2050. A use rate of 50% corresponds to the global average and a use rate of 64% considers potential re-treatment scenarios, as indicated by the 2013 Collaboration for Cancer Outcomes Research and Evaluation (CCORE) radiotherapy use rate model. We established specified requirements for teletherapy units at a ratio of 1:450 patients, for radiation oncologists at a ratio of 1:250 patients, for medical physicists at a ratio of 1:450 patients, and for radiation therapists at a ratio of 1:150 patients in all countries and consistently using these ratios. We collected current country-level data on the radiotherapy-professional workforce from national health reports, oncology societies, or other authorities from 32 countries.

FINDINGS: In 2022, there were an estimated 20·0 million new cancer diagnoses, with approximately 10·0 million new patients needing radiotherapy at an estimated use rate of 50% and 12·8 million at an estimated use rate of 64%. In 2050, GLOBOCAN 2022 data indicated 33·1 million new cancer diagnoses, with 16·5 million new patients needing radiotherapy at an estimated use rate of 50% and 21·2 million at an estimated use rate of 64%. These findings indicate an absolute increase of 8·4 million individuals requiring radiotherapy from 2022 to 2050 at an estimated use rate of 64%; at an estimated use rate of 50%, the absolute increase would be 6·5 million individuals. Asia was estimated to have the highest radiotherapy demand in 2050 (11 119 478 [52·6%] of 21 161 603 people with cancer), followed by Europe (3 564 316 [16·8%]), North America (2 546 826 [12·0%]), Latin America and the Caribbean (1 837 608 [8·7%]), Africa (1 799 348 [8·5%]), and Oceania (294 026 [1·4%]). We estimated that the global radiotherapy workforce in 2022 needed 51 111 radiation oncologists, 28 395 medical physicists, and 85 184 radiation therapists and 84 646 radiation oncologists, 47 026 medical physicists, and 141 077 radiation therapists in 2050. We estimated that the largest proportion of the radiotherapy workforce in 2050 would be in upper-middle-income countries (101 912 [38·8%] of 262 624 global radiotherapy professionals).

INTERPRETATION: Urgent strategies are required to empower the global health-care workforce and facilitate the fundamental human right of access to suitable health care. A collective effort with innovative and cost-contained health-care strategies from all stakeholders is warranted to enhance global accessibility to radiotherapy and address challenges in cancer care.

FUNDING: China Medical Board Global Health Leadership Development Program, Shanghai Science and Technology Committee Fund, China Ministry of Science and Technology Department of International Cooperation High Level Cooperation and Exchange Projects, and Fudan University Office of Global Partnerships Key Projects Development Fund.