Introduction:

Nearly 20% of metastatic castration-resistant prostate tumors carry germline or somatic homologous recombination repair (HRR) gene mutations. Molecular testing is recommended by the NCCN for men with advanced prostate cancer as they may be candidates for targeted therapy based on the presence of these mutations. While the prevalence of latent prostate cancer is higher at an earlier age and tends to be more aggressive in men of African descent, the prevalence of genetic mutations among different races is not well established. We aim to identify how many prostate cancer patients treated with systemic therapy had genetic testing, and whether there were any differences based on age or race.

Methods:

We retrospectively collected data from patients with a diagnosis of metastatic prostate cancer treated with systemic therapy at Ochsner Medical Center in New Orleans, LA, between 2015 and 2020. Metastatic prostate cancer diagnosis was confirmed from oncology documentation, pathology, or imaging. Demographics, baseline clinical characteristics, prognostic markers, genetic testing, and type of systemic therapy administered were collected. Chi-squared and Fisher's exact test were performed to compare differences in genetic testing by age and race.

Results:

Of 559 patients with metastatic prostate cancer, 14.1% had genetic testing (Table 1). 2.0% of patients tested had a BRCA2 mutation, and 8.6% had other mutations including BRCA1 (n=2), ATM (n=7), BRIP1 (n=1), BARD1 (n=1), and RAD51D (n=2). Seven patients (1.3%) were treated with a PARP inhibitor [olaparib (n=4), or rucaparib (n=3)]. For prevalence of genetic testing, there was a statistically significant difference in age between Caucasian (mean 71.0) and African American (mean 67.3) patients (Table 2). While there was no significant difference in genetic testing and presence of mutations between races, there was a statistically significant difference in genetic testing by age (<70 yrs: 21.5%, >70 yrs: 6.3%), BRCA2 mutation (<70 yrs: 3.1%, >70 yrs: 0.7%), and other mutations (<70 yrs: 12.8%, >70 yrs: 4.1%) of patients tested (Table 2). Of note 7 patients (1.3%) had microsatellite instability or mismatch repair deficient tumors, with 5 patients receiving immunotherapy.

Conclusion:

Even though genetic testing in prostate cancer may inform prognosis and treatment options, have implications for family counseling, and is strongly recommended by national guidelines, only a minority of patients underwent testing at our institution. Additional strategies are needed to increase the prevalence of genetic testing in men with advanced prostate cancer, and we need further larger-scale studies to determine differences in predictive markers based on age and race. Developing these strategies and workflows is important to ensure equity with genetic testing for all ages and races. Further analyses will also be useful to determine the cost-benefit analysis of genetic testing, as well as the real-world impact of novel therapies such as PARP inhibitors and immunotherapies on prostate cancer outcomes.

Funding: N/A