Regression and growth rates in androgen deprivation therapy for advanced castration-sensitive prostate cancer

No study has compared cancer regression (d) and growth (g) rates in patients with advanced castration-sensitive prostate cancer (CSPC) treated with androgen deprivation therapy. The comparison of d and g rates provides insight into the differential impact of ADT regimens on tumor dynamics, potentially guiding more personalized treatment strategies. Therefore, we aimed to estimate these rates and evaluate their impact on survival outcomes.

Sequential prostate-specific antigen (PSA) data was obtained from the KYUCOG-1401 trial including patients with advanced CSPC randomized to gonadotropin-releasing hormone (GnRH) antagonist (group A) and GnRH agonist plus bicalutamide (group B). d and g rates were estimated by applying mathematical models and were compared in subgroups. PSA-progression-free survival (PSA-PFS), radiographic progression-free survival (rPFS), and overall survival (OS) were compared by lower and higher than the median of these rates.

Patients with higher PSA and higher extent of disease score at enrollment presented higher d rates (0.03965 vs. 0.03546, p = 0.0006) and (0.03947 vs. 0.03587, p = 0.0113) for groups A and B, respectively. The median d rate was lower for group A than group B (0.03306 vs. 0.039965, respectively [p = 0.0002]). The median g rate was higher for group A than group B (0.00016 vs. 0.00002, respectively [p = 0.0014]). The g rate, but not the d rate discriminated PSA-PFS, rPFS, and OS.

Our results suggest that GnRH agonist plus bicalutamide reduced PSA level faster and suppressed PSA rising longer than GnRH antagonist. Moreover, measuring the g rate can predict PSA-PFS, rPFS, and OS in patients with advanced CPSC treated with androgen deprivation therapy. These findings suggest that incorporating g rate measurements into clinical practice could improve prognostic accuracy and guide treatment decisions in advanced CSPC.