Abstract LB130: High adherence to mammography screening before and after MCED testing

Abstract Background: Multi-cancer early detection (MCED) tests have the potential to detect cancers that do not have screening options. However, there is concern that implementation of MCED tests could lead to a lack of adherence to recommended single cancer screening. We examined mammography screening rates before and after MCED testing in a cohort of individuals eligible for breast cancer screening. Methods: Deidentified data for a US cohort of women with a negative (“no cancer signal detected”) MCED (Galleri®, GRAIL, Inc. ) test administered during a 1-year ascertainment period (7/01/2022-6/30/2023) were linked via tokenization to the Komodo Research Dataset. This analysis focused on women aged 42-72 years with no prior Galleri test, no positive Galleri test result during ascertainment, and with closed health insurance claims coverage on the index test date. A final study sample requiring ≥24 months of continuous coverage before and after the index test was created to capture women eligible for two complete cycles of mammography screening across the observation period. Diagnostic and screening mammograms were identified by billing codes on insurance claim records. Descriptive statistics of test recipients’ demographic characteristics were calculated by mammogram receipt before and/or after the index MCED test. Results: Of the 6, 122 women in the eligible population, 2, 820 (46. 1%) were in the final study sample. Women in the study sample had similar demographics as the eligible population, with mean age of 57. 3 years, 61. 9% white non-Hispanic, and 80. 4% commercial health insurance. 2, 317 (82. 2%) and 2, 357 (83. 6%) had mammograms in the 24-month pre- and post-index periods, respectively. 2, 108 (74. 8%) women had mammograms in both periods, while 254 (9. 0%) did not have a mammogram in either period (Table). Conclusions: Women maintained high adherence to mammography at 24 months following receipt of a negative MCED test result, with 80% of women receiving mammograms in that period. Citation Format: Charles H. McDonnell, Gretchen M. Stipec, Arushi Chadha, Anuraag R. Kansal, Claire O'Connell, Alice Kate Cummings Joyner, Andrew J. Epstein, Eric T. Fung, A. Mark Fendrick. High adherence to mammography screening before and after MCED testing abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86 (8Suppl): Abstract nr LB130.