Temporal Evolution and Diagnostic Diversification of Patients Receiving Proton Therapy in the United States: A Ten-Year Trend Analysis (2012 to 2021) From the National Association for Proton Therapy

Purpose/Objective(s) The XXXX conducted eight surveys of all operational United States proton centers (2012-2021), analyzing patients treated, diagnoses, treatment complexity, to evaluate trends and diversification of patients receiving proton therapy. Materials/Methods Detailed surveys were sent in 2015, which requested data on 2012-2014, then annually to active proton centers in the US. Patient numbers treated at each center for the preceding calendar year(s) were collated for tumors in the following categories: central nervous system (CNS), intraocular, pituitary, skullbase/skeleton, head/neck, lung, retroperitoneal/soft tissue sarcoma, pediatric (solid tumors in children age ≤18), gastrointestinal tract, urinary tract, female pelvic, prostate, breast and “other.” Complexity levels were assessed using CPT codes 77520-77525. Results Survey response rates were excellent (100% in 2015 to 94.9% in 2021); additional publicly available information provided near complete information on all centers. Trend comparisons between 2012 and 2021 showed that the total annual number of patients treated with protons gradually increased from 5,377 to 15,829. The largest numeric increases were for head/neck (316 to 2,303; 7.3-fold), breast (93 to 1,452; 15.6-fold) and gastrointestinal (170 to 1,259; 7.4-fold). Patient numbers also increased significantly for central nervous system (598 to 1,743; 2.9-fold), pediatric (685 to 1,870; 2.7-fold), and skull base (179 to 514; 2.9-fold). For prostate cancer, the percentage of proton-treated patients decreased from 43.4% to 25.0% of the total. Simple compensated treatments decreased from 43% in 2012 to 7% in 2021, whereas intermediate complexity treatments increased from 45% to 73%. Conclusion The number of patients treated with protons is gradually increasing, with a substantial proportionate decline in patients with prostate cancer receiving proton therapy. The number of patients treated for “commonly accepted” indications for protons - pediatric, CNS, and skull base - is gradually increasing. Greater proportional increases were observed for breast, lung, head/neck, and gastrointestinal tumors. Treatment complexity is gradually increasing over time.