Utilization of liquid biopsy for advanced gastrointesinal malignancies in a community oncology practice.

Abstract

127 Background: Liquid biopsy (LB) offers a non-invasive alternative for obtaining genomic signature of malignancies to develop a tailor-made treatment plan. We evaluated the feasibility and impact on clinical management of liquid biopsies performed on patients with advanced gastrointestinal malignancies in a community setting. Methods: A retrospective chart review of adult patients with stage-IV gastrointestinal malignancies was conducted to gather all the pertinent information, including diagnoses, treatment regimens, results of liquid biopsies and any impact on further management. Results: Data on 42 liquid biopsies performed between Aug 2018 and Mar 2020 was collected. M:F ratio was 1.4: 1. Median age was 57yrs (range 31-86). The diagnoses were; Colo-rectal Ca 22(54.7%), pancreatic 9(21.9%), gastric 2(4.7%), biliary 2(4.7%), HCC 2(4.7%), Appendix 1 (2.3%), CUP 1(2.3%) and others 3(7.1%). One (2.3%) LBs was done before first line treatment and 41(97.7%) were done after the failure of first line treatment. There was insufficient sample in the bx to do tissue-NGS for the pt. who had LB before starting treatments. Majority of LBs, 37(88%) were done after the failure of second line/later treatments compared to 5(12%) done after failing the first line treatment. Patient preference and technical challenge to obtain adequate tissue were the commonest reasons for getting the LBs. Results were available in all (100%) the cases. Median turnaround time was 8 days (range:7-13). The commonest mutations were TP53,APC, KRAS, PIK3CA, BRAF, SMAD4. BRCA-2 was identified in 1 pancreatic ca pt. MSI-H was noted in 3 patients; 2 with Colon ca, and 1 with CUP. An actionable alteration was seen in, 40 (95.2%) of the patients. A FDA approved target-matched drug was available for 27/40(67.5%) pts., if we also consider off-label usage. For those who had an alteration, but no FDA approved target-matched drug was available, 13/40 (32.5%), a clinical trial was available for all 13/13 (100%) of the pts.. 43% of those who had a FDA approved target-matched treatment available, but not approved for their disease, were able to receive the drug off-protocol. Two out of 13(15.3%) of the pts. who had a clinical trial available, were enrolled on a study. Conclusions: Liquid biopsies can be efficiently utilized in a community oncology practice. It offers an attractive option to gather genomic information of malignant cells in patients with advanced GI malignancies to be able to deliver state of the art care to all patients, including those who may not have a convenient access to a tertiary center.