Patient-reported Outcomes After External Beam Radiotherapy With Low Dose Rate Brachytherapy Boost vs Radical Prostatectomy for Localized Prostate Cancer: Five-year Results From a Prospective Comparative Effectiveness Study

Abstract

Purpose: Data comparing radical prostatectomy and external beam radiation therapy with low dose rate brachytherapy boost are lacking. To better guide shared decision making regarding treatment, we compared patient reported outcomes through 5 years following radical prostatectomy or external beam radiation therapy with low dose rate brachytherapy boost for localized prostate cancer.

Materials and methods: From 2011-2012, men aged <80 years with localized prostate adenocarcinoma were enrolled and followed longitudinally. Patient reported outcomes included the Expanded Prostate Index Composite. Regression models adjusted for baseline scores and covariates were constructed.

Results: The study population included 112 men treated with external beam radiation therapy with low dose rate brachytherapy boost and 1,553 treated with radical prostatectomy. Compared to radical prostatectomy, external beam radiation therapy with low dose rate brachytherapy boost was associated with clinically meaningful worse urinary irritative/obstructive (adjusted mean score difference [95% confidence interval]: 5.0 [-8.7, -1.3]; P = .008 at 5 years) and better urinary incontinence function (13.3 [7.7, 18.9]; P < .001 at 5 years) through 5 years. Urinary function bother was similar between groups (P > .4 at all timepoints). Treatment with external beam radiation therapy with low dose rate brachytherapy boost was associated with worse bowel function (-4.0 [-6.9, -1.1]; P = .006 at 5 years) through 5 years compared to radical prostatectomy. Treatment with external beam radiation therapy with low dose rate brachytherapy boost was associated with better sexual function at 1 year (12.0 [6.5, 17.5]; P < .001 at 1 year) compared to radical prostatectomy, but there was insufficient evidence to reject the supposition that no difference was seen at 3 or 5 years.

Conclusions: Compared to radical prostatectomy, external beam radiation therapy with low dose rate brachytherapy boost was associated with clinically meaningful worse urinary irritative/obstructive and bowel functions but better urinary incontinence function through 5 years after treatment. These patient-reported functional outcomes may clarify treatment expectations and help inform treatment choices for localized prostate cancer.

Keywords: brachytherapy; patient reported outcome measures; prostatectomy.

Figure 1:

Unadjusted Expanded Prostate Cancer Index Composite and Short Form Domain Scores Comparing EBRT-LDR vs. RP Through Five Years Unadjusted domain scores (ranging from 0–100 with higher scores reflecting better function) were tracked at baseline, 6 months, 1 year, 3 years, and 5 years for EPIC and SF36 surveys. Panels (A) through (E) reflect the EPIC domains such as urinary irritation, urinary incontinence, bowel function, sexual function, and hormone function. Panels (F) through (H) reflect the SF36 domains such as physical function, emotional well-being, and energy/fatigue. All EPIC domains were well-balanced at baseline with the exception of sexual function which was lower in the EBRT-LDR group vs. RP group (65 points [quartiles: 33, 85] vs. 78 points [38, 95]; P=0.016). All SF36 domains were well-balanced at baseline with the exception of emotional well-being which was higher in the EBRT-LDR group vs. RP group (86 points [80, 92] vs. 84 points [68, 92]; P=0.009). Abbreviations: External beam radiotherapy plus low-dose brachytherapy (EBRT-LDR); radical prostatectomy (RP); 26-item Expanded Prostate Cancer Index Composite (EPIC); 36-item Short Form (SF36).

Figure 2:

Adjusted Expanded Prostate Cancer Index Composite Domain Scores Comparing EBRT-LDR vs. RP Through Five Years Adjusted domain scores for EPIC function (ranging from 0–100 with higher scores reflecting better function) were represented through radar plots by comparing baseline to (A) 6 months, (B) 1 year, (C) 3 years, and (D) 5 years in the EBRT-LDR group (blue line) vs. RP group (red line). The EPIC minimum clinically important difference scores were 5–7 points for urinary irritative/obstructive function, 6–9 points for urinary incontinence, 4–6 points for bowel function, 10–12 points for sexual function, and 4–6 points for hormone function. The outermost part of the radar plot represents best function (score of 100) and the center represents worst function (score of 0). The adjusted domain scores were generated by applying a multivariable linear regression model that accounts for baseline scores and other covariates. EBRT-LDR, when compared to RP, was associated with a clinically meaningful decline in urinary irritative/obstructive function (−5-point difference [95% CI −8.7, −1.3]; P=0.008) and bowel function (−4-point difference [95% CI −6.9, −1.1]; P=0.006) through 5 years. RP, when compared to EBRT-LDR, was associated with a clinically meaningful decline in urinary incontinence (−13.3-point difference [95% CI −7.7, −18.9]; P<0.001) through 5 years and sexual function (−12-point difference [95% −6.5, −17.5]; P<0.001) through 1 year. Abbreviations: External beam radiotherapy plus low-dose brachytherapy (EBRT-LDR); radical prostatectomy (RP); 26-item Expanded Prostate Cancer Index Composite (EPIC); 36-item Short Form (SF36); 95% confidence interval (95% CI).

Figure 3:

Adjusted Short Form Domain Scores Comparing EBRT-LDR vs. Radical Prostatectomy Through Five Years Adjusted domain scores for SF36 function (ranging from 0–100 with higher scores reflecting better function) were represented through radar plots by comparing baseline to (A) 6 months, (B) 1 year, (C) 3 years, and (D) 5 years in the EBRT-LDR group (blue line) vs. RP group (red line). The SF36 minimum clinically important difference scores were 7 points for physical function, 6 points for emotional well-being, and 9 points for energy/fatigue. The outermost part of the radar plot represents best function (score of 100) and the center represents worst function (score of 0). The adjusted domain scores were generated by applying a multivariable linear regression model that accounts for baseline scores and other covariates. There were no clinically meaningful changes in SF36 function between the two groups through 5 years. Abbreviations: External beam radiotherapy plus low-dose brachytherapy (EBRT-LDR); radical prostatectomy (RP); 36-item Short Form (SF36).