EMBARK post hoc analysis of impact of treatment suspension (TxS) on health-related quality of life (HRQoL).

5005 Background: EMBARK (NCT02319837) showed enzalutamide (ENZ) + leuprolide (L) and ENZ mono delayed metastasis-free survival vs placebo (P) + L while maintaining high global HRQoL in high-risk biochemically recurrent nonmetastatic hormone-sensitive prostate cancer. Treatment was suspended (TxS) at week 37 if PSA <0.2 ng/mL; reinstated if PSA rose to ≥2.0 ng/mL with radical prostatectomy (RP) or ≥5.0 ng/mL without RP. This analysis examined HRQoL after TxS. Methods: Longitudinal change in HRQoL from new baseline, week 37 (time of TxS), to subsequent assessments until week 205 were assessed via mixed model repeated measures using separate models for each instrument. Intention to treat analysis was used. Results: Treatment was suspended in 90.9% (321/353), 85.9% (304/354), and 67.8% (240/354) of patients treated with ENZ + L, ENZ mono, and P + L, respectively. A numerical trend inHRQoL improvement after week 37 TxS was seen in all 3 arms, which often reached clinically meaningful threshold at week 205 (Table). Post TxS, all arms reached clinically meaningful improvement in hormonal treatment side effects at the subsequent assessments of week 49 to week 97; however, patients slowly deteriorated, with clinically meaningful deterioration at week 205 relative to week 37 with ENZ + L and P + L. No statistically significant differences were observed between arms in change from week 37 to week 205. Conclusions: This post hoc analysis confirmed that TxS, as expected, leads to clinically meaningful improvements in HRQoL. Clinical trial information: NCT02319837 . Table: see text