A population-based assessment of proton beam therapy utilization in California

Proton beam therapy (PBT) is a type of radiation therapy (RT) used for certain cancer types because it minimizes collateral tissue damage. The high cost and limited availability of PBT have constrained its utilization. This study examined patterns and determinants of PBT use in California. Persons with diagnoses of all cancer types from 2003 to 2016 inclusive who had any type of RT were identified in the California Cancer Registry in this retrospective analysis. Cross-tabulations were performed to summarize the demographic characteristics of the study population, both for individuals who received PBT and for those who received other RT modalities. PBT use patterns over time were assessed. Multivariate logistic regression models assessed the effects of demographics and health insurance type on receipt of PBT. Of the 2,499,510 people with a cancer diagnosis during the study period, 578,632 (23%) received some type of RT, and of these, 8609 received PBT (1.5%). PBT was most often used to treat cancers of the prostate (41.3%), breast (14.0%), eye (11.7%), lung (6.1%), and brain (6.0%). PBT use was highest in 2003-2004 and then declined over time. PBT use was significantly associated with being white or male, younger age, higher socioeconomic status, Medicare or dual Medicare-Medicaid insurance, uninsured/self-pay status, and proximity to treatment. Significant differences exist in PBT use by demographics and health insurance type. The identified racial and socioeconomic disparities merit further investigation. More granular studies on both use patterns and effectiveness of PBT for specific cancers are needed to draw stronger conclusions about its cost-benefit ratio.