Abstract 617P
Background
Circulating tumor DNA (ctDNA) is an emerging resource for the diagnosis and prognosis of various types of cancer. However, characteristics and clinical utility of ctDNA is still largely unknown, especially in patients with genitourinary (GU) cancers.
Methods
SCRUM-Japan consortium of Nationwide Cancer Genome Screening Project has started MONSTAR-SCREEN project which evaluates ctDNA for patients with advanced solid tumors since Apr 2019 in Japan. We collected plasma and tumor samples in patients with prostate cancer (PC), urothelial carcinoma (UC), and renal cell carcinoma (RCC). Plasma ctDNA and tumor genomic DNA were analyzed by a NGS-based ctDNA assay, Foundation One® Liquid (F1L) and tissue-based panel, Foundation One® CDx (F1CDx), respectively.
Results
As of Sep 2020, 639 patients with advanced solid tumors were enrolled in MONSTAR-SCREEN. Among them, we analyzed 92 ctDNA samples of advanced GU cancers (43 PC, 27 UC, and 22 RCC) and compared the feature in GU cancers with that in non-GU cancers. The level of ctDNA in GU cancers was similar to that in non-GU cancers (median 1.92% vs. 3.80%, P = 0.229). Although UC possessed the highest median blood tumor mutation burden (bTMB) in all cancers (4.39), there was no significant bTMB difference between GU cancers and non-GU cancers (2.63 vs. 2.63, P = 0.995). Interestingly, the mutation rate in genes related to DNA damage response pathway was significantly higher in GU cancers compared to that in non-GU cancers (32.6 % vs. 19.7%, P = 0.00879). When we focus on other major oncogenic signaling pathways such as PI3K, MAPK and Wnt-signal pathway, we found that related genes in these pathways were less frequently altered in GU cancer versus non-GU cancers (P = 0.017, P < 0.001 and P = 0.00327, respectively). We also assessed concordance between liquid biopsy and tumor tissue-based sequencing and found that two-thirds of detected variants in F1L were overlapped with that in F1CDx.
Conclusions
For the first time, we performed comprehensive genomic profiling of ctDNA in GU cancers. We further evaluate ctDNA profiling before and after starting cancer treatments and connect these data to clinical trials.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
SCRUM-Japan MONSTAR-SCREEN.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.