Minimal residual disease (MRD) test utilization in the first 6 months after initiating MRD testing in patients with colorectal cancer (CRC).

e15710 Background: With high levels of postoperative circulating tumor DNA (ctDNA) identified as a potential predictor of CRC recurrence, clinical studies are ongoing to obtain evidence to support using ctDNA results to determine risk features for consideration of adjuvant therapy in stage II CRC. As MRD tests emerge to measure ctDNA in CRC, this study aimed to describe utilization of MRD tests and subsequent systemic cancer therapies in the first 6 months after initiating MRD testing in patients with CRC. Methods: Using de-identified administrative claims data in Optum Labs Data Warehouse, commercial and Medicare Advantage (MA) enrollees were identified with ≥1 MRD test (based on CPT codes and unique identifier test codes submitted on claims) with a CRC diagnosis code from 01/01/2021 to 08/31/2023 (index date = first MRD test). Additional inclusion criteria were continuous enrollment in the 360-day baseline and 180-day follow-up periods, ≥1 baseline diagnosis for CRC, and no baseline evidence of an MRD claim or another primary cancer. Patients were stratified into 1 of 3 hierarchical groups based on intended use case inferred from claims data: 1) advanced disease (≥1 baseline claim with ICD-10 C77*-C80.0); 2) non-advanced post-surgery (without advanced disease and ≥1 baseline claim with a surgery procedure and CRC diagnosis code); or 3) non-advanced non- surgery (remaining patients). Outcomes included the number MRD tests, time between tests, and use of systemic cancer therapies in the 180- day follow-up after index date. Results: Of 1420 patients (median 71y, 51% male, 83% MA) with MRD tests, 41% were advanced, 32% non-advanced post-surgery, and 27% non-advanced non-surgery. In follow-up (Table), the groups had significant differences in the number of MRD tests (p < 0.001), days between 1 st , 2 nd , and 3 rd tests (p < 0.05), and use of systemic cancer therapy (p < 0.001). Patients with advanced disease received the highest number of MRD tests and had the most frequent use of systemic cancer therapies, followed by non-advanced post-surgery, and then by non-advanced non-surgery. Conclusions: In the first 6 months after initiating MRD testing in CRC, utilization varied by intended use. More MRD tests were administered with advanced disease or non-advanced disease post-surgery than without advanced disease or surgery. Further research is needed to assess MRD use in patients with low- and high-risk features over a longer follow-up and therapy changes after MRD results. Use of MRD tests and therapies in the 180-day follow-up. AdvancedN = 587 Non-advanced post-surgeryN=452 Non-advanced non-surgeryN=381 Number of MRD tests, mean (SD)* 2.3 (1.2) 2.1 (1.0) 1.7 (0.9) 1* 27% 31% 47% 2 36% 35% 40% 3* 24% 25% 10% 4+* 12% 9% 3% Days from 1 st to 2 nd test, median* 86 81 93 Days from 2 nd to 3 rd test, median** 56 57 75 Days from 3 rd to 4 th test, median 45 49 48 Use of systemic cancer therapy* 54% 27% 17% *p<0.001, **p=0.04.