Comprehensive Genome Profiling-Initiated Tumor-Informed Circulating Tumor DNA Monitoring for Patients With Advanced Cancer

In Japan, comprehensive genome profiling (CGP) as a companion diagnostic (CDx) has been covered by public insurance since June 2019, but the proportion of patients with cancer who actually received drug therapy based on CGP data is low. In the present study, we attempted to use CGP as a starting point for tumor-informed circulating tumor DNA (ctDNA) monitoring. We retrospectively validated 219 patients with malignant tumors who underwent CGP at Iwate Medical University Hospital between October 2019 and April 2023 in terms of patient demographics, genetic analysis, drug recommendations, and drug administration rate. The 219 cancer cases analyzed by CGP for 27 target organs, including prostate (n = 27, 12.3%), colorectal (n = 25, 11.4%), lung (n = 19, 8.7%), and other neoplasms (n = 148, 67.6%). Among the cohort, only 14 cases (6.4%) subsequently were able to undertake the recommended action by Molecular Tumor Board. Of patients who underwent ctDNA monitoring based on somatic mutations identified by CGP (n = 11), clinical validity was confirmed in terms of early relapse prediction (n = 5, 45.5%), treatment response evaluation (n = 10, 90.9%), and no relapse/regrowth corroboration (n = 2, 18.2%) whereas 90.9% (n = 10) of patients obtained information with at least one source of the clinical validity. Although the current rate of CGP contributing to a drug recommendation is low, CGP results can be an alternate resource for tumor-informed longitudinal ctDNA monitoring to provide information concerning early relapse prediction, treatment response evaluation, and no relapse/regrowth corroboration.