Abstract 666P
Background
We have recently demonstrated that a salvage therapy with carboplatin plus weekly docetaxel is effective in docetaxel-refractory prostate cancer (PC) and interferes with testosterone biosynthesis (Reuter et al.; Oncol Res & Treat. 2018, 41 (suppl.1): p.10). In this study, the impact of docetaxel monotherapy on free and total testosterone serum levels (fT, TT) and the prognostic role of fT and TT were analyzed in mPC patients.
Methods
59 consecutive mPC patients were treated with at least two cycles of docetaxel (75 mg/m2 q3w; 50 mg/m2 q2w, or 35 mg/m2 q1w) until disease progression, occurrence of intolerable adverse effects or completion of the planned cycle number. Efficacy measures were done following PCWG2 recommendations. FT and TT were measured before and during chemotherapy.
Results
At the current analysis, the median follow-up time was 20.8 months. Response of prostate-specific antigen (PSAR; ≥50% PSA reduction) was observed in 39/59 (66.1%) and 11/37 (29.7%) patients with measurable disease exhibited a partial remission (PR). Median progression-free survival (PFS) for all patients was 7.8 months (CI 95% 3.8, 11.8) and median overall survival (OS) was 25.1 months (CI 95% 17.6, 32.7). The most common reversible grade 3/4 toxicity was leukopenia/neutropenia (29.3/34.5%). Median fT and TT serum levels were reduced below the detection limit during docetaxel treatment (fT: from 0.37 pg/mL to <0.01 pg/mL and TT: from 0.12 to <0.05 ng/mL, respectively). Multivariate Cox regression analyses identified fT nadir values <0.01 pg/mL, PSAR>50%, number of organs involved and previous prednisone treatment as independent prognostic risk factors for PFS and fT reduction >90%, number of organs involved and previous prednisone as independent prognostic risk factors for OS. FT nadir values <0.01 pg/mL and PSAR >50% were associated with longer PFS (p<0.05). Additionally, docetaxel-induced reduction of free testosterone >90% was associated with longer PFS and OS (p<0.05).
Conclusions
These data demonstrate that fT is an important prognostic factor for PFS and OS in mPC patients.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.