Clinical utility of next generation sequencing (NGS) on circulating tumor DNA (ctDNA) in patients (pts) with pancreatic cancer (PC).

Abstract

4154 Background: ctDNA provides opportunities for identifying targeted therapies, a source to conduct NGS when tissue acquisition is infeasible, detection of minimal residual disease (MRD), and identification of resistance mutations. There are limited large data sets to inform clinical utility and limited correlation of NGS of ctDNA and tumor in PC. Herein, we evaluate the ctDNA detection rate in multiple cohorts of PC and report the ctDNA-tissue genotype concordance in PC at Memorial Sloan Kettering (MSK). Methods: Pts with PC at MSK who had ctDNA prospectively collected using the MSK-ACCESS 129 gene ctDNA NGS assay, were identified. ctDNA detection was defined as the identification of a mutation, copy number (no.) alteration or structural variant. Tissue-based NGS using MSK-IMPACT gene assay was performed for pts with adequate tissue, and matched with ctDNA by date. Clinical, pathologic and outcome data were abstracted. Data are summarized with descriptive statistics. Overall survival (OS) estimated by Kaplan-Meier method from date of ctDNA draw to death/last follow up. Results: From 08/2019 to 07/2022, N= 414 pts with PC and ≥ 1 ctDNA sample included. Median age 69 years (range 29-92), female N=206 (50%). Stage at ctDNA collection: Stage I-III N= 203 (49%); Stage IV N= 211 (51%). ctDNA detection rate by no. of involved organs; 0 organs (MRD), N=7/30 (23%); 1-2 organs, N=158/270 (58.5%); 3-4 organs, N=82/102 (80.4%); >5 organs, 12/12 (100%). CtDNA detection rate by site of metastasis; Liver only, 75/99 (76%); peritoneum only, 15/25 (60%); lung only, 10/22 (45%). In pts with detected ctDNA median CA 19-9 was 494 U/mL (range 0, 247674) vs 100 U/mL (range 1, 22360) in pts with undetected ctDNA. In pts with detected ctDNA median CEA was 7 ng/mL (range 1, 2020) vs 4 ng/mL (range 1, 99) in pts with undetected ctDNA. In stage IV untreated pts, median OS 13 months(m) (95% CI; 7.3, 16) and 10 m (95% CI; 5.6, -) for ctDNA detected vs undetected, respectively. ctDNA detection rates by stage, and concordance between ctDNA and tissue-based NGS for common driver mutations KRAS, TP53, CDKN2A and SMAD4 in N=131 matched pairs are summarized in the table. Conclusions: ctDNA detection rates are high (89%) in pts with untreated stage IV PC, with high concordance between ctDNA and tissue-based NGS (87% - 95%). In untreated stage I-III PC, detection and concordance rates are lower (<50%). Detection rates are associated with disease burden, site of metastasis, CA 19-9/CEA levels. ctDNA is a promising tool in detection of somatic alterations in PC, particularly in stage IV disease, and is a complementary adjunct to tumor-based NGS. [Table: see text]