Disparities in Specialized Radiation Treatment Modalities for Grade Group 2, Intermediate-Risk Prostate Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Men with Grade Group 2 (GG2) intermediate risk (IR) prostate cancer (PCa) have multiple curative radiation (RT) options. Compared to conventional external beam photon RT (XRT), including 3D-conformal RT (3DCRT) and IMRT, highly conformal RT techniques may provide less integral RT dose to normal tissue, including brachytherapy (BT), SBRT, and proton beam radiation therapy (PBT). These treatments require either advanced equipment and/or specialized training. Here we analyzed national trends in utilization of XRT, BT monotherapy, SBRT, and PBT, and assessed potential factors associated with receiving each technique. We hypothesize that socioeconomic and/or racial disparities are associated with differences in utilization of these specialized techniques. <h3>Materials/Methods</h3> Men diagnosed with favorable IR PCa cancer, defined as Gleason 3+4 disease, PSA < 20 and clinical stage T1-T2 N0 M0, between 2004-2017 were identified in the National Cancer Database. Cohorts were defined as: XRT (3DCRT+IMRT, hypofractionated (HF) or standard fractionation (SF)), BT monotherapy (HDR, LDR), SBRT (5 fx) and PBT (HF or SF). Trends in utilization were examined. Associations between technique and patient, clinical disease, and sociodemographic characteristics were assessed by multivariable logistic regression, with <i>P</i><0.05 considered significant. <h3>Results</h3> 71,140 patients met inclusion criteria of which 72.4% received standard XRT and 27.6 % received specialized radiation modalities (18.5% brachytherapy, 6.0% SBRT, & 3.1% PBT). Utilization of XRT and BT declined from 71.0% (XRT) and 27.5% (BT) in 2004 to 69.7% (XRT) and 17.2% (BT) in 2017. Receipt of SBRT and PBT increased from 0% (SBRT) and 1.45% (PBT) in 2004 to 9.9% (SBRT) and 3.3% (PBT) in 2017, respectively. On multivariable logistic regression, Black patients were less likely to receive BT (adjusted OR 0.79; 95%CI 0.74-0.83), SBRT (adjusted OR 0.77; 95%CI 0.70-0.85), or PBT (adjusted OR 0.39; 95%CI 0.33-0.47) compared to XRT (all <i>P</i><0.0001). Socially disadvantaged seniors (SDS; age >65 years with Medicaid insurance) were less likely to receive specialized RT (adjusted OR 0.45; 95%CI 0.31-0.60; P<0.0001). Factors associated with increased likelihood of receiving BT, SBRT, or PBT included: treatment at Academic/Research center, treatment at a metropolitan facility, younger age, lower Charlson-Deyo Comorbidity Score, and lower PSA at presentation (all P < 0.01). <h3>Conclusion</h3> Trends in utilization of RT modalities have dramatically changed in recent years with a sharp decline in BT, a doubling of PBT, and rapid adoption of SBRT, as coded in the NCDB. Compared to White patients with GG2 IR PCa, there are disparities in utilization of BT, SBRT, and PBT for Black patients and for SDS. It is unclear whether similar disparities exist for other prostate cancer grade groups for which BT and SBRT are being utilized. Future efforts should address access-to-care challenges for the use of these specialized techniques as they are expanded into higher GG.