Impact of PSA nadir, PSA response and time to PSA nadir on overall survival in real-world setting of metastatic hormone-sensitive prostate cancer patients

Background: To evaluate the impact of prostate-specific antigen (PSA) nadir, PSA response and time to PSA nadir (TTN) in metastatic hormone-sensitive prostate cancer (mHSPC) patients on overall survival (OS) in the era of combination therapies.

Methods: Different PSA nadir cut-offs (including ultra-low PSA) were tested for OS analyses. Additionally, PSA response ≥99% was evaluated, as well as TTN categorized as <3 versus 3-6 versus 6-12 versus >12 months. Multivariable Cox regression models predicted the value of PSA nadir cut-offs, PSA response and TTN on OS. Sensitivity analyses were performed in de novo and high volume mHSPC patients.

Results: Of 238 eligible patients, PSA cut-offs of <0.2 versus 0.2-4.0 versus >4.0 ng/mL differed significantly regarding median OS (96 vs. 56 vs. 44 months, p < 0.01), as well as in subgroup analyses of de novo mHSPC patients and multivariable Cox regression models. A more stringent PSA cut-off of <0.02 versus 0.02-0.2 versus >0.2 ng/mL also yielded significant median OS differences (not reached vs. 96 vs. 50 months, p < 0.01), even after additional multivariable adjustment. A PSA response ≥99% was also significantly associated with better OS than counterparty with <99% response, even after multivariable adjustment (both p < 0.02). When TTN groups were compared, patients with longer TTN harbored more extended OS than those with short TTN (<3 vs. 3-6 vs. 6-12 vs. >12 months: 34 vs. 50 vs. 67 vs. 96 months, p < 0.01). Virtually similar results were observed in sensitivity analyses for high volume mHSPC patients.

Conclusions: In times of combination therapies for mHSPC, a PSA nadir of respectively, <0.2 and <0.02 ng/mL are associated with best OS rates. Moreover, a relative PSA response ≥99% and a longer TTN are clinical important proxies for favorable OS estimates.