Kaltman, Rebecca

LBA10509 Background: The MCED test (Galleri) detects a shared cancer signal from cell-free DNA in blood and predicts a cancer signal origin (CSO) to guide diagnostic (dx) workup. PF2 (NCT05155605) is a large, prospective, multicenter, interventional study of the MCED test’s performance and safety in a diverse US intended-use population. Methods: PF2 enrolled participants aged ≥50y without clinical suspicion of cancer or cancer diagnosis/treatment within 3y of enrollment. Primary objectives were MCED performance and safety in terms of dx testing triggered by a positive (cancer signal detected) MCED test result. Participants with a positive MCED test underwent targeted dx workup guided by the predicted CSO(s). Participant-reported anxiety was assessed with the State Trait Anxiety Inventory. Results: PF2 enrolled 35,878 participants; 32,007 with a 12m cancer assessment were analyzable for performance. Of 287 (0.9%) with a positive MCED test, 173 were diagnosed with cancer within 12m, for a cancer detection rate of 0.5% (95% CI 0.5-0.6%) and positive predictive value of 60.3% (54.5-65.8%). Specificity was 99.6% (99.6-99.7%). 12m episode sensitivity was 69.8% (62.8-76.0%) in a prespecified subgroup of 12 cancers responsible for ⅔ of US cancer deaths, 66.2% (55.1-75.8%) in a subgroup of 6 aggressive cancers with low 5y survival, and 39.3% (34.9-44.0%) across all cancers. Overall CSO prediction accuracy was 91.3% (86.2-94.7%) across all cancers. The MCED test detected 151 new primary and 22 recurrent cancers; additional cancers detected by screening were those with USPSTF A/B (n=31) and C (n=60) recommended screening. Of 151 MCED-detected new primaries, 80 (53.0%) were clinical stage I-II; 107 (70.9%) were stage I-III. Of 80 MCED-detected stage I-II cancers, 71.2% had no USPSTF A/B screening recommendation. Of 35,335 participants analyzable for safety, 213 (0.6%) had invasive procedure(s) to evaluate a positive MCED test result, of which 90% were nonsurgical and 1.8x more likely for participants with vs without cancer diagnosis. Most (87.6%) had a CSO-guided dx evaluation. There were 5 study-related adverse events during the time of dx workup; none were serious. Anxiety temporarily increased for participants with a positive MCED test and cancer diagnosed, and returned to baseline by 12m. Of participants with a positive MCED test, median time from test result to dx resolution was 48d (95% CI 43-56). Few participants (7/63 [11.1%]) had cancer found by dx PET/CT after a targeted dx workup that did not reveal cancer. Conclusion: The MCED test demonstrated robust performance with a favorable safety profile. When MCED testing was added to USPSTF A/B screening, 6.5x more cancers were detected by screening, most at early stages. The diverse, representative PF2 participant population supports the generalizability of these findings to the US intended-use population. Clinical trial information: NCT05155605 .