Patient Reported Outcomes Following Proton Pencil Beam Scanning vs. Passive Scatter/Uniform Scanning for Localized Prostate Cancer: Secondary analysis of PCG 001-09

Abstract Background Although pencil beam scanning (PBS) is the most conformal method for proton beam therapy (PBT) delivery, it is unknown if outcomes differ compared to treatment with passive scatter/uniform scanning (PS/US). This analysis compares patient reported outcomes (PRO) changes following PBS and PS/US for prostate cancer (PC) in a prospective multicenter registry study. Methods We evaluated PROs with the Expanded Prostate Cancer Index Composite (EPIC) instrument for men with localized PC enrolled in PCG 001-09 (NCT01255748). PROs were assessed at baseline and through 12 months of follow-up. We compared mean changes in EPIC scores, as well as the proportions of men experiencing a one- and two-fold minimally important difference (MID) in domain scores, between PBS and PS/US. Multivariate analyses (MVAs) were performed to further evaluate the association between proton modality and PRO changes. Results Three-hundred-and-four men completed EPIC at baseline; 72 received PBS and 232 received PS/US. The average quality-of-life (QOL) declines from baseline through 12 months did not significantly differ between the two groups. The proportion of men reporting a 1-MID decline at 12 months for PBS and PS/US was 34.3% and 27.4%, respectively, for urinary QOL (P=0.27); 40. 1% and 40.9% for bowel QOL (P=0.36); and 30. 1% and 36.6% for sexual QOL (P=0.94). Corresponding 2-MID declines for PBS and PS/US were observed in 26.9% and 13.2% of men for urinary QOL (P=0.01), 35.3% and 29.1% for bowel QOL (P=0.33); and 16.4% and 18.1% for sexual QOL (P=0.76). The association between proton modality and 2-MID changes in urinary QOL at 12-months remained significant on MVA (P=0.007). Conclusions The results of this analysis show differences between PBS and PS/US with regards to two-fold MID changes in urinary function at 12 months, but no differences for average score declines over time. Future studies evaluating PRO measures between the two PBT modalities are warranted.