Pattern of Radiotherapy Treatment for Prostate Cancer (PCa) Patients: Analysis of a Hospital Based Registry

Purpose/Objective(s) Prostate Cancer (PCa) is the most common cancer among males and is the second leading cause of cancer related mortality. Definitive radiation therapy (RT) plays an important role in curative intent treatment for localized prostate cancer. RT can be delivered with various radiation techniques depending on availability of resources and patient-specific criteria. The aim of this study was to compare the utilization of various RT techniques using a large, national hospital-based registry. Materials/Methods We analyzed an extensive data set of N0, M0, non-surgical PCa patients diagnosed between 2004 and 2015 using National Cancer Database (NCDB). Patients were grouped into six categories based on RT modality: (1) IMRT with brachytherapy (BT) boost (n=12,734), (2) IMRT only (n=106,246), (3) Proton therapy (n=4,561), (4) SBRT (n=7,533), (5) LDR BT (n=45,452), and (6) HDR BT (n=23,400). Patients were also stratified according to the NCCN guidelines: low-risk (c_stage T1-T2a, Gleason Score (GS) ≤ 6, Prostate-Specific Antigen (PSA) < 10), intermediate-risk (c_stage T2b or T2c, GS of 7, PSA of 10-20), and high-risk (c_stage T3-T4, GS of 8-10, PSA > 20). Overall survival (OS) probability was determined using a Kaplan-Meier estimator. Univariate and multivariate analyses of patient characteristics were performed by risk group for the six treatment modalities. Results The most commonly used treatment modality for PCa patients was IMRT (53.1%) across the risk groups. In the low-risk group, IMRT and LDR BT were utilized in a similar proportion (35.0%). A steady increase of SBRT utilization was observed (from 0% in 2004 to over 10% in 2015 for low- and intermediate-risk patients), while HDR BT usage declined markedly. Highest OS probability was observed for the proton therapy group, while SBRT, LDR BT, HDR BT, and IMRT+BT had similar survival probabilities. IMRT was associated with the lowest OS. Higher median incomes (HR=0.63, p<0.01), treatment at academic/research facilities (HR=0.83, p<0.01), and increased distance of residence from treatment facility (HR=0.94, p<0.01) were some factors with strongest association to increased overall survival. Conclusion This study revealed that IMRT was the most common RT modality for PCa patients over the study period, with a steady increase in SBRT technique and decline in BT. The rate of utilization for each RT modality was not representative of its corresponding median OS in the studied population. The association of improved OS with proton therapy, higher median income, and increased distance from treatment facility all suggest that health care disparities and selection biases are largely responsible for the differences observed, both by the clinicians' offering of select modalities and the patients' access to pursue certain therapy. Future management of PCa patients via radiotherapy modalities would likely benefit from randomized clinical trials and longer observation periods.