This study evaluated PROs with the Expanded Prostate Cancer Index Composite (EPIC) instrument for men with localized PC enrolled in PCG 001-09 (NCT01255748) that were treated with proton PBS or PS/US. Three-hundred-and-four men completed EPIC at baseline (72 received PBS and 232 received PS/US). This study 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.

The proportion of men reporting a 1-MID decline at 12 months for PBS and PS/US was 34.3% and 27.4% 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 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.