# Evaluation of Second-Line Treatment for Castration-Resistant Prostate Cancer following the Administration of Upfront Androgen Receptor Signaling Inhibitors

## TL;DR

This study found that using androgen receptor signaling inhibitors as second-line treatment for prostate cancer after initial use may be more effective than docetaxel, especially when abiraterone is used first.

## Contribution

The study provides new evidence on the effectiveness of treatment sequences for castration-resistant prostate cancer.

## Key findings

- Median progression-free survival was longer with androgen receptor signaling inhibitors than docetaxel in second-line treatment.
- Abiraterone as first-line treatment was a prognostic factor for better progression-free survival.
- The abiraterone–enzalutamide sequence showed better outcomes than other sequences.

## Abstract

This study evaluated the effects of docetaxel and androgen receptor signaling inhibitors as second-line treatments in patients with castration-resistant prostate cancer after androgen receptor signaling inhibitors as first-line treatment. This study retrospectively evaluated the clinical outcomes of second-line treatment with docetaxel or androgen receptor signaling inhibitor in patients with castration-resistant prostate cancer who received first-line treatment with androgen receptor signaling inhibitors. Clinical backgrounds and outcomes were compared between docetaxel and androgen receptor signaling inhibitors as second-line treatment. Of 59 patients, 21 (35.6%) and 38 (64.4%) received docetaxel and androgen receptor signaling inhibitors as second-line treatment after first-line treatment with androgen receptor signaling inhibitors, respectively. In the second-line setting, the median progression-free survival was longer with androgen receptor signaling inhibitor than with docetaxel (17 versus 6 months, P=0.014). In the first-line setting, the median progression-free survival was longer with androgen receptor signaling inhibitors than with docetaxel (32 versus 25 months, P=0.014); however, no significant difference was found in the overall survival. Multivariate analysis revealed that there was no significant association between second-line treatment and survival, and first-line treatment with abiraterone was identified as a prognostic factor for progression-free survival. Subgroup analysis showed that the abiraterone–enzalutamide sequence was more effective than the other three sequences for progression-free survival and overall survival. This study suggests that second-line treatment with an androgen receptor signaling inhibitor for castration-resistant prostate cancer after androgen receptor signaling inhibitors as first-line treatment may be more beneficial, particularly with abiraterone as the upfront treatment.