Five‐year outcomes from a prospective comparative effectiveness study evaluating external‐beam radiotherapy with or without low‐dose‐rate brachytherapy boost for localized prostate cancer
Authors: Pasalic Dario , Barocas Daniel A. , Huang Li‐Ching , Zhao Zhiguo , Koyama Tatsuki , Tang Chad , Conwill Ralph , Goodman Michael , Hamilton Ann S. , Wu Xiao‐Cheng , Paddock Lisa E. , Stroup Antoinette M. , Cooperberg Matthew R. , Hashibe Mia , O’Neil Brock B. , Kaplan Sherrie H. , Greenfield Sheldon , Penson David F. , Hoffman Karen E. 
Published: February 2021

Background

To inform patients who are in the process of selecting prostate cancer treatment, the authors compared disease‐specific function after external‐beam radiotherapy (EBRT) alone versus EBRT plus a low‐dose‐rate (LDR) brachytherapy boost (EBRT‐LDR).

Methods

For this prospective study, men who had localized prostate cancer in 2011 and 2012 were enrolled. Assessments at baseline, 0.5, 1, 3, and 5 years included the patient‐reported Expanded Prostate Index Composite, the 36‐item Medical Outcomes Study Short‐Form Health Survey, and treatment‐related regret. Regression models were adjusted for baseline function and for patient and treatment characteristics. The minimum clinically important difference in scores on the Expanded Prostate Index Composite 26‐item instrument was from 5 to 7 for urinary irritation and from 4 to 6 for bowel function.

Results

Six‐hundred ninety‐five men met inclusion criteria and received either EBRT (n = 583) or EBRT‐LDR (n = 112). Patients in the EBRT‐LDR group were younger (median age, 66 years [interquartile range [IQR], 60‐71 years] vs 69 years [IQR, 64‐74 years]; P < .001), were less likely to receive pelvic radiotherapy (10% vs 18%; P = .040), and had higher baseline 36‐item Medical Outcomes Study Short‐Form Health Survey physical function scores (median score, 95 [IQR, 86‐100] vs 90 [IQR, 70‐100]; P < .001). Over a 3‐year period, compared with EBRT, EBRT‐LDR was associated with worse urinary irritative scores (adjusted mean difference at 3 years, −5.4; 95% CI, −9.3, −1.6) and bowel function scores (−4.1; 95% CI, −7.6, −0.5). The differences were no longer clinically meaningful at 5 years (difference in urinary irritative scores: −4.5; 95% CI, −8.4, −0.5; difference in bowel function scores: −2.1; 95% CI, −5.7, −1.4). However, men who received EBRT‐LDR were more likely to report moderate or big problems with urinary function bother (adjusted odds ratio, 3.5; 95% CI, 1.5‐8.2) and frequent urination (adjusted odds ratio, 2.6; 95% CI, 1.2‐5.6) through 5 years. There were no differences in survival or treatment‐related regret between treatment groups.

Conclusions

Compared with EBRT alone, EBRT‐LDR was associated with clinically meaningful worse urinary irritative and bowel function over 3 years after treatment and more urinary bother at 5 years.

Lay Summary

In men with prostate cancer who received external‐beam radiation therapy (EBRT) with or without a brachytherapy boost (EBRT‐LDR), EBRT‐LDR was associated with clinically worse urinary irritation and bowel function through 3 years but resolved after 5 years.

Men who received EBRT‐LDR continued to report moderate‐to‐big problems with urinary function bother and frequent urination through 5 years.

There was no difference in treatment‐related regret or survival between patients who received EBRT and those who received EBRT‐LDR.

These intermediate‐term estimates of function may facilitate counseling for men who are selecting treatment.