Evolution of biomarker testing in advanced non-small cell lung cancer (aNSCLC) and metastatic breast cancer (mBC) in U.S. community practices.

e18778 Background: Biomarker testing has advanced from single-gene to NGS. This study examined aNSCLC and mBC biomarker testing ≤ 90d of advanced (adv) or metastatic (met) diagnosis (Dx) and treatment (tx) patterns at US practices. Methods: A retrospective observational study used Flatiron Health electronic health-record-derived de-identified database at OneOncology (OO) community and non-OO Flatiron Health nationwide (NAT) sites (̃90% community, ̃10% academic). Patients (Pts) ≥ 18y, with Dx of aNSCLC or mBC from 1/1/18 - 4/30/21, with ≥ 1 visit ≤ 90d after adv/met Dx and ≥ 90d follow-up were evaluated. Descriptive analyses and logistic regression were used. Results: A total of 16,882 pts with aNSCLC (2366 OO; 14,516 NAT), and 6500 pts with mBC (1026 OO; 5474 NAT) were included. Overall testing was high and stable (OO: 85% aNSCLC, 98% mBC; NAT: 84%, 97%) with higher NGS testing at OO (58% aNSCLC; 28% mBC) vs NAT (49%; 16%) (Table), which reflected more pts with aNSCLC tested for all 6 mutations (ALK, BRAF, KRAS, ROS-1, EGFR, PD-L1; 54% OO vs 50% NAT, p<0.001) and more pts with mBC tested for PIK3CA (27% OO vs 16% NAT, p<0.001). In aNSCLC, NGS testing increased similarly for OO and NAT over time (p>0.05); mBC NGS testing increased faster at NAT vs OO (p<0.05). Of pts tested and treated, 16% aNSCLC (1945 OO; 11,376 NAT) and < 3% mBC (14 OO; 108 NAT) received tx before test results were available. For pts with aNSCLC with ≥ 1 actionable mutation (ALK, BRAF, ROS-1, EGFR), 18% OO and 22% NAT had tx before test results. Cancer immunotherapy plus chemotherapy was the most common tx (36 % OO vs 40 % NAT); after test results, 33% vs 56% OO and 45% vs 44% NAT pts stayed on tx vs switched to targeted tx. For pts with aNSCLC with ≥ 1 aforementioned actionable mutations who waited until test results were available, 65% received targeted tx at OO and NAT. Conclusions: Biomarker testing has become standard of care in aNSCLC and mBC in US community settings. NGS rates increased over time and were higher at OO vs NAT. Differences in pts treated before test results reflects the need to wait for NGS results to inform initial tx in aNSCLC vs non-NGS results for mBC. This study shows NGS testing in US community practices has increased since 2018, particularly in mBC, but opportunities remain to optimize NGS results into tx decisions.[Table: see text]