Comparative effectiveness study of patient-reported outcomes after proton therapy or intensity-modulated radiotherapy for prostate cancer

Abstract

Background: Data continue to emerge on the relative merits of different treatment modalities for prostate cancer. The objective of this study was to compare patient-reported quality-of-life (QOL) outcomes after proton therapy (PT) and intensity-modulated radiation therapy (IMRT) for prostate cancer.

Methods: A comparison was performed of prospectively collected QOL data using the Expanded Prostate Cancer Index Composite (EPIC) questionnaire. QOL data were collected during the first 2 years after treatment for men who received PT and IMRT. PT was delivered to 1243 men at a single center at doses from 76 grays (Gy) to 82 Gy. IMRT was delivered to 204 men who were included in the Prostate Cancer Outcomes and Satisfaction with Treatment Quality Assessment (PROSTQA) study in doses from 75.6 Gy to 79.4 Gy. The Wilcoxon rank-sum test was used to compare EPIC outcomes by modality using baseline-adjusted scores at different time points. Individual questions were assessed by converting to binary outcomes and testing with generalized estimating equations.

Results: No differences were observed in summary score changes for bowel, urinary incontinence, urinary irritative/obstructive, and sexual domains between the 2 cohorts. However, more men who received IMRT reported moderate/big problems with rectal urgency (P = 0.02) and frequent bowel movements (P = 0.05) than men who received PT.

Conclusions: There were no differences in QOL summary scores between the IMRT and PT cohorts during early follow-up (up to 2-years). Response to individual questions suggests possible differences in specific bowel symptoms between the 2 cohorts. These outcomes highlight the need for further comparative studies of PT and IMRT.

Keywords: genitourinary; intensity-modulated radiotherapy; outcomes; prostate cancer; proton therapy.

Figure 1

Expanded Prostate Cancer Index Composite (EPIC) summary scores over time for men treated with intensity-modulated radiotherapy or proton therapy for prostate cancer. Bar and whisker graphs at baseline and 6 months, 1 year, and 2 years after proton therapy or intensity-modulated radiotherapy for A) bowel summary score, B) urinary incontinence score, C) urinary irritative/obstructive score, and D) sexual summary score (no androgen deprivation therapy). The bottom whisker represents the cut-off for the score of the lowest 5%, the bottom bar represents the cut-off score for the lowest quartile, the blue line represents the median score, the top of the bar represents the cut-off for the top quartile, and the top of the whisker represents the cut-off for the score of the top 5%. At the bottom of the graph the asterisk (*) represents a statistically significant change from baseline score for each treatment modality and time point, while a pound sign (#) represents a statistically significant and minimally detectable (>50% of the baseline standard deviation) change from the baseline score.

Figure 1

Expanded Prostate Cancer Index Composite (EPIC) summary scores over time for men treated with intensity-modulated radiotherapy or proton therapy for prostate cancer. Bar and whisker graphs at baseline and 6 months, 1 year, and 2 years after proton therapy or intensity-modulated radiotherapy for A) bowel summary score, B) urinary incontinence score, C) urinary irritative/obstructive score, and D) sexual summary score (no androgen deprivation therapy). The bottom whisker represents the cut-off for the score of the lowest 5%, the bottom bar represents the cut-off score for the lowest quartile, the blue line represents the median score, the top of the bar represents the cut-off for the top quartile, and the top of the whisker represents the cut-off for the score of the top 5%. At the bottom of the graph the asterisk (*) represents a statistically significant change from baseline score for each treatment modality and time point, while a pound sign (#) represents a statistically significant and minimally detectable (>50% of the baseline standard deviation) change from the baseline score.

Figure 1

Expanded Prostate Cancer Index Composite (EPIC) summary scores over time for men treated with intensity-modulated radiotherapy or proton therapy for prostate cancer. Bar and whisker graphs at baseline and 6 months, 1 year, and 2 years after proton therapy or intensity-modulated radiotherapy for A) bowel summary score, B) urinary incontinence score, C) urinary irritative/obstructive score, and D) sexual summary score (no androgen deprivation therapy). The bottom whisker represents the cut-off for the score of the lowest 5%, the bottom bar represents the cut-off score for the lowest quartile, the blue line represents the median score, the top of the bar represents the cut-off for the top quartile, and the top of the whisker represents the cut-off for the score of the top 5%. At the bottom of the graph the asterisk (*) represents a statistically significant change from baseline score for each treatment modality and time point, while a pound sign (#) represents a statistically significant and minimally detectable (>50% of the baseline standard deviation) change from the baseline score.

Figure 1

Expanded Prostate Cancer Index Composite (EPIC) summary scores over time for men treated with intensity-modulated radiotherapy or proton therapy for prostate cancer. Bar and whisker graphs at baseline and 6 months, 1 year, and 2 years after proton therapy or intensity-modulated radiotherapy for A) bowel summary score, B) urinary incontinence score, C) urinary irritative/obstructive score, and D) sexual summary score (no androgen deprivation therapy). The bottom whisker represents the cut-off for the score of the lowest 5%, the bottom bar represents the cut-off score for the lowest quartile, the blue line represents the median score, the top of the bar represents the cut-off for the top quartile, and the top of the whisker represents the cut-off for the score of the top 5%. At the bottom of the graph the asterisk (*) represents a statistically significant change from baseline score for each treatment modality and time point, while a pound sign (#) represents a statistically significant and minimally detectable (>50% of the baseline standard deviation) change from the baseline score.