National trends and determinants of proton therapy use for prostate cancer: A National Cancer Data Base study

BACKGROUND In the current study, the authors sought to both characterize the national trends in proton therapy use for prostate cancer and determine the factors associated with receipt of this limited resource, using what to the best of their knowledge is the largest nationwide cancer registry. METHODS The National Cancer Data Base was used to identify 187,730 patients diagnosed with nonmetastatic prostate cancer from 2004 through 2012 who received external beam radiotherapy as their initial form of definitive therapy. Multivariable logistic regression analysis adjusted for sociodemographic and clinical factors was used to identify independent determinants of proton therapy use. RESULTS The rate of proton therapy use increased significantly from 2.3% in 2004 to 5.2% in 2011 and 4.8% in 2012 (P value for trend <.0001). Proton therapy for prostate cancer was much more likely to be delivered at an academic compared with nonacademic center and to patients who were white, younger, healthier, from metropolitan areas, from zip codes with higher median household incomes, and who did not have an advanced stage of or high-grade disease (all P<.0001). Compared with white patients, those who were black and Hispanic were found to be significantly less likely to receive proton therapy even after robust multivariable adjustments (adjusted odds ratio, 0.20 [95% confidence interval, 0.18-0.22; P<.0001] and adjusted odds ratio, 0.57 [95% confidence interval, 0.48-0.66; P<.0001], respectively). CONCLUSIONS The use of proton therapy to treat patients with prostate cancer more than doubled from 2004 to 2012, with striking racial disparities in its use noted despite robust multivariable adjustments. Long-term follow-up is needed to determine whether the increased use of proton therapy for prostate cancer is justified, and ongoing efforts should be made to ensure equal access to resource-limited oncologic therapies.