Development and Independent Validation of a Prognostic Gene Expression Signature Based on RB1, PTEN, and TP53 in Metastatic Hormone-sensitive Prostate Cancer Patients

Abstract

Background: Androgen deprivation therapy (ADT) with docetaxel (D) and/or antiandrogen receptor therapies (ARTs) are the standard therapies in metastatic hormone-sensitive prostate cancer (mHSPC). Alterations in the tumor suppressor genes (TSGs) RB1, PTEN, and TP53 are associated with an aggressive evolution and treatment resistance in castration-resistant prostate cancer (CRPC).

Objective: To study the clinical implications of TSG mRNA expression in mHSPC patients.

Design, setting, and participants: This is a multicenter retrospective biomarker study in mHSPC patients. TSG_low status was defined when two or more out of the three TSGs presented low RNA expression by nCounter in formalin-fixed paraffin-embedded samples and TSG_wt for the remaining cases. The microarray data from the CHAARTED trial were analyzed as an independent validation cohort.

Outcome measurements and statistical analysis: Molecular data were correlated with CRPC-free survival (CRPC-FS) and overall survival (OS) by the Kaplan-Meier method and multivariate Cox analysis.

Results and limitations: A total of 226 patients were included, of whom 218 were eligible: 93 were treated with ADT and 125 with ADT + D; 75.7% presented de novo stage IV and 67.9% high-volume disease. TSG_low (19.2%) was independently correlated with shorter CRPC-FS (hazard ratio [HR] 1.8, p = 0.002) and OS (HR 2, p = 0.002). In the CHAARTED trial, TSG_low was independently correlated with lower CRPC-FS (HR 2.2, p = 0.02); no differences in clinical outcomes according to treatment were observed in TSG_low patients, while a significant benefit was observed for ADT + D in the TSG_wt group for CRPC-FS (HR 0.4, p < 0.001) and OS (HR 0.4, p = 0.001). However, no interaction was observed between TSG signature and treatment in either series. Study limitations are the retrospective design, small sample size, and lack of inclusion of patients treated with ADT + ART.

Conclusions: TSG_low expression correlates with adverse outcomes in patients with mHSPC. The investigation of new therapeutic strategies in these patients is warranted.

Patient summary: The low RNA expression of tumor suppressor genes in the tumors is correlated with adverse outcomes in patients with metastatic hormone-sensitive prostate cancer.

Keywords: Androgen deprivation therapy; Biomarkers; CHAARTED trial; Docetaxel; Hormone-sensitive prostate cancer; Tumor suppressor genes.