Tamsulosin–mirabegron combo improves urination frequency but not voiding volume

Treatment with the combination of tamsulosin plus mirabegron following ¹²⁵I-brachytherapy for prostate cancer falls short of improving voiding volume compared with tamsulosin monotherapy, although the combination helps with urination frequency and overactive bladder symptoms, according to a study.

A total of 240 patients who underwent ¹²⁵I-brachytherapy for prostate cancer (cT1-cT3aN0M0) in a single institution were randomized to receive subsequent therapy with the combination of tamsulosin (0.2 mg/day) plus mirabegron (50 mg/day; n=122) or tamsulosin alone (n=118) for lower urinary tract symptoms.

The primary endpoint of change from baseline in mean voided volume per micturition 3 months after ¹²⁵I brachytherapy was similar between the two treatment groups: −62.5 with the combination therapy and −68.0 with monotherapy (p=0.17).

In terms of the secondary endpoints, there were some significant between-group differences noted. Specifically, the combination vs the monotherapy group showed markedly favourable improvements in the Overactive Bladder Symptom Score (p=0.02) and the 24-hour urinary frequency (p=0.03) at 3 months.

Retention rates within 3 months after ¹²⁵I-brachytherapy were comparable: 7.3 percent (9/122) in the combination group and 6.0 percent (7/118) in the monotherapy group (p=0.80).

The findings suggest that the combination of tamsulosin plus mirabegron may be preferable to tamsulosin monotherapy for reducing the frequency of urination and overactive bladder symptoms among prostate cancer patients treated with ¹²⁵I-brachytherapy who are experiencing lower urinary tract symptoms.