(P004) A Retrospective Study to Assess Disparities in the Utilization of Intensity-Modulated Radiotherapy (IMRT) and Proton Therapy (PT) in the Treatment of Prostate Cancer (PCa)

April 30, 2015

Disparities exist in PT utilization compared with IMRT by age, race, and SES and merit further investigation.

Kristina L. Demas, MD, Neha Vapiwala, MD, Stefan Both, PhD, Curtiland Deville, MD; University of Pennsylvania

BACKGROUND: Despite its increase in use, proton therapy (PT) is a relatively limited resource. The purpose of this study was to examine clinical and demographic differences in intensity-modulated radiotherapy (IMRT) and PT utilization for prostate cancer (PCa).

METHODS: All patients with low- and intermediate-risk PCa (n = 350) undergoing definitive RT (2.5 Gy × 28 fractions or 1.8 Gy ×44 fractions) between 2010–2012 at a single institution were divided into IMRT (n = 58) and PT (n = 292) comparison groups. Pretreatment characteristics, including age, race, socioeconomic status (SES) (low vs high, defined as geocoded census tract 20% below or above poverty level, respectively), prostate-specific antigen (PSA), clinical tumor stage, Gleason score, risk group, prostate volume, and patient-reported outcomes, were retrospectively collected. Chi-square and independent sample t-tests were used for analyses.

RESULTS: Of PT patients, 228 (78%), 51 (18%), 4 (1%), and 9 (3%) were white, black, Asian, or other, respectively; 256 patients (88%) had high SES, and 36 (12%) had low SES. Mean age, distance from center, PSA level, prostate volume, International Prostate Symptom Score (IPSS), and International Index of Erectile Function (IIEF) in the PT group were 65 ± 7.1 years, 86 ± 190 miles, 5.6 ± 2.9 ng/mL, 41 ± 18 cc, 8 ± 6, and 19 ± 6, respectively; 142 (49%) patients were low-risk, and 150 (51%) were intermediate-risk. A total of 236 (81%), 46 (16%), and 10 (3%) PT patients were T1c, T2a, and T2b, respectively; 154 (53%) and 138 (47%) patients were Gleason 6 and 7.

In the IMRT group (n = 58), 28 (48%), 24 (42%), 3 (5%), and 3 (5%) patients were white, black, Asian, or other, respectively; 40 (69%) patients had higher SES, and 18 (31%) had low SES. Mean age, distance, PSA, prostate volume, IPSS, and IIEF were 69 ± 8.6, 16 ± 18 miles, 7.4 ± 4.5 ng/mL, 54 ± 40 cc, 8 ± 7, and 14 ± 8, respectively; 142 (49%) were low-risk, and 150 (51%) were intermediate-risk patients. A total of 236 (81%), 46 (16%), and 10 (3%) IMRT patients were T1c, T2a, and T2b, respectively; 154 (53%) and 138 (47%) patients were Gleason 6 and 7.

The cohorts varied in average age (P = .0005), race (P < .0001), SES status (P = .0007), and average miles traveled to the facility (P = .0054)-ie, IMRT patients were older, resided closer, and consisted of more black and low-SES patients. Baseline PSA (P = .0001), Gleason score (P = .0244), prostate volume (P = .0040), and IIEF (P < .001) were significantly increased for IMRT, while risk group, T stage, and IPSS were not (P > .05 for all). Therapeutically, IMRT patients were less likely to receive hypofractionated therapy (P < .0001) and more likely to receive androgen deprivation therapy (P = .0006).

CONCLUSION: Disparities exist in PT utilization compared with IMRT by age, race, and SES and merit further investigation.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org