Prediction of undetectable circulating tumor DNA by comprehensive genomic profiling assay in metastatic prostate cancer: the SCRUM-Japan MONSTAR SCREEN project.

Background: Undetectable circulating tumor DNA (ctDNA) is an obstacle to performing comprehensive genomic profiling in daily practice to identify genomic alterations. We investigated the associations between clinicopathological factors and undetectable ctDNA using a commercially available comprehensive genomic profiling assay in metastatic prostate cancer. Patients and methods: Patients treated with systemic treatment for metastatic prostate cancer were included. ctDNA was analyzed by FoundationOne^®Liquid CDx at enrollment. The associations between clinicopathological characteristics and ctDNA detection were analyzed. Results: The number of bone metastasis was associated with ctDNA detection (odds ratio [95% confidence interval], 13.6 [1.71–108], P = 0.014). An algorithm predicting ctDNA detection using clinicopathological parameters was created. If ≥ 4 bone metastases were observed, ctDNA detection was estimated to be 98.9%. Among the patients with < 4 bone metastases, if two or three features among ISUP grade group 5, PSA level ≥ 10 ng/ml, and castration resistance were present, the ctDNA detection rate was 96.7% while the ctDNA detection rate was 86.3% if no or only one feature was present. Conclusions: An algorithm created in this study is helpful in determining when to undertake comprehensive genomic profiling assay using blood. [ABSTRACT FROM AUTHOR]