3742 - Prognostic value of tumor suppression genes (TP53, PTEN, Rb) in metastatic hormone sensitive prostate cancer

Background

Loss of tumour suppressor genes (TSGs), TP53, PTEN and Rb are common in advanced prostate cancer. They are associated with worse outcomes in hormone-resistant prostate cancer. However, the prognostic value of TSGs loss in metastatic hormone-sensitive prostate cancer (mHSPC) is unknown. Therefore we sought to evaluate the prognostic value of TSGs loss on progression-free survival (PFS) in mHSPC.

Methods

We performed a retrospective analysis of patients with mHSPC treated at Mayo Clinic Arizona between 2015 and 2018. Clinical characteristics, first-line treatment, and TSGs alterations were recorded. TSG-altered (TSG-alt) was defined as an alteration in ≥ 1 TSG (TP53, PTEN or Rb). Demographics and clinical characteristics were compared between groups by chi-square test for frequency data or Kruskal Wallis rank-sum test for continuous measures. PFS was estimated based on the Kaplan-Meier method and compared between groups by the log-rank test.

Results

59 patients with mHSPC were included. 41 (69%) patients received first-line treatment with abiraterone and 18 (31%) patients with docetaxel. 32 patients (54%) had TSG-alt. 20 patients (39%) had damage to 1 TSG, 11 patients (19%) had damage to 2 TSGs, and 1 patient had damage to all 3. Clinical characteristics, prior locoregional treatment, and metastatic disease on diagnosis were similar between TSG-alt and TSG-normal groups. The rate of damaging alterations to the genes was: TP53 21 patients (35.6%), PTEN 21 patients (35.6%), and Rb 3 patients (5.1%). Median PFS was 33.2 mos (95% CI 23.1-NE) for TSG-normal versus 19.7 mos (95% CI 14.4-30.0) for TSG-alt, p = 0.005. There was no difference in PFS between having 1 TSG alteration (18.4 mos; 95% CI 14.7 - NE) vs ≥ 2 TSG alterations (21.8 mos; 95% CI 10.6 - NE) or between first-line treatments with abiraterone (20.2 mos; 95% CI 14.7-35.1) vs docetaxel (19.6 mos; 95% CI 8.0 - NE) in those with TSG-alt.

Conclusions

Loss of TSGs function is common in patients with mHSPC, and is prognostic for early progression during first-line treatment. The presence of ≥ 1 TSG-alt indicates an adverse prognostic impact in mHSPC. Confirmation of these findings may establish the need for inclusion of molecular stratification when defining high risk mHSPC patients.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Mayo Clinic Cancer Center.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.