(P-575) Impact of Treatment Sequence on Survival Outcome in Patients with a Second Treatment Line for Metastatic Castration-resistant Prostate Cancer: A New-user Design in the French Nationwide Claims Database

Background: Abiraterone acetate in association with prednisone/prednisolone and docetaxel can both be used as first- or second-line treatments for metastatic castration-resistant prostate cancer (mCRPC).

Objectives: To assess whether starting with an abiraterone acetate first line followed by a docetaxel second line (ABI – DOCE sequence) or to use the reverse sequence DOCE-ABI has an impact on survival outcome in mCRPC patients in real life.

Methods: A new-user cohort study design with a 3-year follow-up: patients initiating a first-line treatment for mCRPC in 2014 followed by a second treatment line were identified from the French nationwide claims database (SNDS), which covers about 86% of the population at the time of the study. Patients with sequence ABI–DOCE and those with DOCE-ABI were 1:1 matched on prostate cancer stage before mCRPC status, duration from prostate cancer diagnosis, and a high-dimensional propensity score. The 36-month overall survival (OS) and the 36-month survival time until treatment switch or death (discontinuation-free survival, proxy of progression-free survival) were, compared using Cox proportional hazards risk model.

Results: Out of the 3 949 mCRPC patients that initiated a first-line treatment in 2014, 1162 died during this first line, and 2283 had a second-line treatment. Among them, 693 received the sequence ABI–DOCE and 354 DOCE–ABI. A total of 159 patients per group were 1:1 matched. The median duration of the first treatment line was 8.4 months in the ABI–DOCE sequence and 6.6 months in the DOCE–ABI sequence. The median duration of the second line was 6.3 months and 6.5 months in the ABI–DOCE and DOCE–ABI sequences, respectively. Around 60% of the patients received a third-line treatment in both groups. The 36-month OS probabilities were 33.8% [27.4 – 41.7] for ABI-DOCE and 34.4% [7.8 – 42.5] for DOCE-ABI with medians survivals of respectively 26.2 months [22.2 – 29.8] and 26.6 months [22.6 – 30.5] (p-value: 0.91). The 36-month discontinuation-free survival probabilities were 13.7% [9.6 – 19.7] for ABI-DOCE and 9.9% [6.4 – 15.1] for DOCE-ABI with medians survivals of respectively 17.5 months [15.4 – 18.9] and 16.1 months [14.5 – 17.6] (p-value: 0.1983).

Conclusions: In real life settings, treatment sequences (ABI–DOCE versus DOCE–ABI) seem to have no differential impact on survival outcome in mCRPC patients sharing same characteristics.