Timely BRCA mutation testing in patients with metastatic prostate cancer: A comparative analysis between Medicare Advantage and traditional Medicare.

319 Background: BRCA mutations have emerged as critical biomarkers for guiding the use of PARP inhibitors in metastatic prostate cancer. Timely access to BRCA testing remains a challenge, especially for those enrolled in Medicare Advantage (MA) plans, which cover more than half of Medicare beneficiaries but often impose greater restrictions than Traditional Medicare (TM). This study compares the timeliness of BRCA testing in patients with metastatic prostate cancer (mPCa) across these two insurance types. Methods: A retrospective cohort study was conducted using the Flatiron Health deidentified Database, including electronic health record-derived data from ~280 cancer practices across the US. Our study population consisted of patients aged 65 or older, diagnosed with mPCa since 2018, and enrolled in either TM or MA. TM and MA were defined as patients enrolled in TM or MA health plans, respectively, either prior to or within 90 days following their mPCa diagnosis. BRCA testing was defined as either germline or somatic testing. We compared the rates of BRCA testing within 45, 90, and 180 days of diagnosis between TM and MA. Given the lack of clinical consensus, we defined timely BRCA testing using three-time windows—45-, 90-, and 180-days post-mPCa diagnosis. Multivariate logistic regression with inverse probability of treatment weighting was used, adjusting for demographics, year of mPCa diagnosis, practice setting, and baseline ECOG performance status. Results: Among the 1,582 MA patients (mean age: 75.9 ± 5.8) and 2,749 TM patients (mean age: 75.4 ± 5.8), significant proportions were from community practice (MA: 78%, TM: 80%) and were characterized by being White (MA: 59%, TM: 65%), aged 75 to 85 (MA: 54%, TM: 57%), having better socioeconomic status (SES 4 or 5: MA: 40.3%, TM: 47.5%), presenting with de-novo mPCa (MA: 53%, TM: 54%), and having better baseline functional performance (ECOG 0 or 1: MA: 70%, TM: 69%). Since 2018, 25.0%, 29.4%, 33.2% of MA patients and 25.9%, 29.1%, 31.9% of TM patients received BRCA testing at 45, 90 and 180 days, respectively. After adjusting for covariates, MA was associated with a 15.2% (OR=0.84, 95%CI 0.73-0.98), 11% (OR=0.89, 95%CI 0.77-1.02), 7.9% (OR=0.92 95%CI 0.80-1.06) lower chance to receive timely BRCA testing within 45 days, 90 days and 180 days, respectively. Conclusions: This study suggests that, compared to TM, mPCa patients enrolled in MA are less likely to receive timely BRCA testing. These findings highlight the needs for further investigation into how Medicare Advantage plans impact cancer care delivery and patient outcomes.