Real-world molecular testing patterns in primary advanced or recurrent endometrial cancer (pA/rEC) in the US.

395 Background: Targeted therapy can improve outcomes in women with pA/rEC, but real-world biomarker testing rates are unknown. This study estimated the real-world proportion of patients receiving biomarker testing (within ≤6 months of advanced/recurrent diagnosis) and characterized testing according to sociodemographic and clinical characteristics. Methods: We used the US Flatiron Health electronic health record–derived deidentified database. Records from 1/1/2013 to 8/31/2023 for women ≥18 years old with advanced/recurrent EC were searched to identify testing for DNA mismatch repair/microsatellite instability (MMR/MSI), HER2, and estrogen or progesterone receptors (ER/PR); a subsample dataset from 4/1/2013 to 11/30/2022 was analyzed for additional biomarkers. The subsample has information on additional biomarker testing and was used to evaluate the frequency of testing for these biomarkers. Testing rates were evaluated using descriptive statistics; characteristics associated with testing were identified by multivariate logistic regression. Results: Among persons meeting eligibility criteria (n=2982), the mean age was 65 years; the majority were non-Hispanic White (56%), had commercial insurance (79%), and received care in a community setting (73%). The subsample (n=509) had similar characteristics to the full cohort. Between 2013-2022, 73% (n=2165) of patients received testing for any biomarker. Testing rates for individual biomarkers are shown in the Table. From 2013 to 2021, testing increased for MMR/MSI (17% to 81%), ER/PR (45% to 62%), and HER2 (15% to 43%). The likelihood of testing was higher among patients with primary advanced EC (OR, 1.45; 95% CI, 1.03-2.06), endometrioid carcinoma histology (1.39; 1.01-1.93), commercial insurance (1.51; 1.18-1.93), at an academic facility (1.70; 1.37-2.11), and with no prior surgery (2.29; 1.83-2.86) relative to other attributes. Conclusions: Molecular testing has increased over time, indicating a continuous trend toward personalized treatment decisions. Several factors associated with an increased likelihood of biomarker testing were identified. Understanding these factors can inform approaches to increase access to molecular testing and increase testing rates. Biomarker testing rates, 2013-2022. Biomarker, n (%) 2013 2021 Overall MMR/MSI a 35 (15) 238 (80) 1604 (54) HER2 a 31 (14) 121 (41) 612 (21) ER/PR a 99 (43) 177 (59) 1465 (49) p53/ TP53 b 13 (36) 31 (74) 260 (51) TMB b 3 (8) 14 (33) 91 (18) CTNNB1 b 4 (11) 12 (29) 88 (17) ARID1A b 4 (11) 15 (36) 91 (18) CDK4/6 b 5 (14) 14 (33) 110 (22) POLE b 4 (11) 17 (40) 110 (22) ARID1A, AT-rich interactive domain-containing protein 1A; CDK4/6, cyclin-dependent kinases 4 and 6; CTNNB1, catenin beta-1; POLE, polymerase-epsilon; TMB, tumor mutation burden. a 2013, n=228; 2021, n=298; overall, n=2982. b Rates from subsample dataset (4/1/2013 to 11/30/2022); 2013, n=36; 2021, n=42; overall, n=509.