Henderson, Randal H.

AbstractBackgroundWe sought to characterize and compare late patient‐reported outcomes (PROs) after moderately hypofractionated intensity modulated radiation therapy (IMRT) and proton beam therapy (PBT) for localized prostate cancer (PC).MethodsThis multi‐institutional analysis included low‐ or intermediate‐risk group PC patients treated with moderately hypofractionated radiation to an intact prostate stratified by treatment modality: IMRT or PBT. The primary outcomes were prospectively collected patient‐reported late gastrointestinal (GI) and genitourinary (GU) toxicity assessed by International Prostate Symptom Score (IPSS) and Expanded PC Index Composite (EPIC). Multivariable regression analysis (MVA) controlling for age, race, and risk group tested the effect of time, treatment, and their interaction.Results287 IMRT and 485 PBT patients were included. Intermediate risk group (81.2 vs. 68.2%; p < 0.001) and median age at diagnosis (70 vs. 67 years; p < 0.001) were higher in the IMRT group. On MVA, there was no significant difference between modalities. PBT IPSS did not differ from IMRT IPSS at 12 months (odds ratio [OR], 1.19; p = 0.08) or 24 months (OR, 0.99; p = 0.94). PBT EPIC overall GI function at 12 months (OR, 3.68; p = 0.085) and 24 months (OR 2.78; p = 0.26) did not differ from IMRT EPIC overall GI function. At 24 months, urinary frequency was no different between PBT and IMRT groups (OR 0.35; p = 0.096).ConclusionsThis multi‐institutional analysis of low‐ or intermediate‐risk PC treated with moderately hypofractionated PBT and IMRT demonstrated low rates of late patient‐reported GI and GU toxicities. After covariate adjustment, late GI and GU PROs were not significantly different between PBT or IMRT cohorts.

e16555 Background: The ProtecT trial underscores the importance of treatment in men with prostate cancer and life expectancies > 10 years and the validity of radiation therapy (RT). RT can be given with photons or protons (PT). To address the controversy of which is better, clinical outcomes of photon-based intensity modulated RT (IMRT) and PT cohorts from 2 institutions were directly compared. Methods: Under respective IRB approvals, data from 2 cohorts were analyzed. The first was 301 men treated with ultrasound image guided IMRT from 2000-05 to 75.6 Gy in 42 fractions. The second was 1214 men treated with fiducial image guided PT from 2006-10 to 78 CGE in 39 fractions. Median age and followup were 74 y and 7.2 y for IMRT and 66 y and 5.6 y for PT. Hormone therapy (ADT) was used with IMRT and PT, respectively, in 3% and 7% of low-risk patients, 25% and 9.9% of intermediate-risk, and 91% and 57.8% of high-risk. Comparative endpoints were age-stratified 5-year (5Y) survival (OS), ≥ grade 3 gastrointestinal (GI) and urologic (GU) toxicity, and 5Y freedom from biochemical progression (FFBP). Results: There was a lower prevalence of GI (1.3% vs 0.1%, p = 0.0065) and GU (4.3% vs 0.1%, p < 0.0001) toxicity at last follow-up in the PT group. In the IMRT and PT cohorts, OS rates were 90.8% and 88.7% in men ≥75 (p = 0.4083). In men < 75, OS rates were 91.6% and 97.5% in the IMRT and PT low-risk patients (p = 0.003), 92.1% and 95.5% in the IMRT and PT intermediate-risk (p = 0.0535), and 92.0% and 90.0% (p = 0.4975) in the IMRT and PT high-risk. In the IMRT and PT cohorts, respectively, FFBP rates were 92.2% and 98.9% for low-risk patients (p < 0.0001), 87.3% and 94.5% for intermediate-risk patients(p = 0.0226), and 80.3% and 74.4% for high-risk patients (p = 0.5154). Conclusions: In this retrospective comparison of outcomes in cohorts of men treated with IMRT and PT for prostate cancer, FFBP rates were better with PT for men with low- and intermediate-risk disease and similar in men with high-risk disease despite longer and more frequent use of ADT in the IMRT cohort. This study underscores the difficulty of comparing retrospective series, with differences noted in age, RT dose, and ADT use between cohorts. However, the magnitude of improvement with PT is intriguing and warrants prospective testing.