Liquid biopsy testing: Impact on treatment assignment and survival in a community-based oncology practice—A real-world experience.

Abstract

3027 Background: Liquid biopsy is a promising, rapid and minimally invasive genetic test examining circulating tumor DNA. It offers a significant potential in selecting signal-matched therapeutic options. Methods: A retrospective chart review was conducted on adult patients with advanced solid cancer whose tumors were tested with the Guardant 360® (Guardant Health) assay between December 2018 and 2019. A follow-up analysis (censor date: 01/06/2021) was carried to assess the actual impact of testing results on treatment assignment and survival. Results: A total of 178 patients underwent testing. Mean age at diagnosis was 65 years. Median (m) Karnofsky Performance Scale was 90% and the majority of patients (89.9%) had ≥ stage III-B disease. Lung (LCa; 50.56%), breast (BCa; 17.42%) and colorectal (CRCa; 7.87%) cancers were the most common cancer types. A positive test was reported in 140/178 patients (78.7%); of those, 105/140 (75%) had an actionable mutation, either with an FDA-approved target-matched therapy (n = 32/105; 30.5%) or with a therapy outside current FDA indication (n = 73/105; 69.5%). In patients with no actionable mutation (n = 35/140; 25%), 85.7% (n = 30/35) had a signal-based clinical trial opportunity. The actual overall signal-based matching rate was 17.8% (24/135; vs. 82.2% no-match rate). Within candidates for FDA-approved treatment, 50% (16/32) received targeted therapy while only 6.9% (5/73) were treated with targeted agents outside current FDA indication: mean matching score (number of matched drugs/number of actionable mutations) was 0.6 (range: 0.33-2) and 0.8 (range: 0.17-2), respectively. Only 10% (3/30) were referred to signal-based clinical trials. Survival analysis of LCa, BCa and CRCa patients with actionable mutations who actually received any therapy (n = 66) revealed post-testing survival advantage for target-matched therapy (n = 22) compared to unmatched therapy (n = 44): overall survival (OS) was longer in the matched cohort (mOS: 13.3 months; 95% CI: 11.8-14.8 vs. 10.7 months; 95% CI: 9-12.4 in unmatched) but did not reach statistical significance ( P = 0.09). Progression free survival (PFS) was significantly longer in patients who received matched therapy (mPFS: 11.3 months; 95% CI: 9.9-12.7 vs. mPFS: 6.8 months; 95% CI: 5.1-8.5 in unmatched; P < 0.05). Conclusions: Implementation of liquid biopsy testing is feasible in community practice and impacts therapeutic choices in patients with advanced malignancies. Receipt of liquid biopsy-generated signal-matched precision therapies conferred added survival benefit compared to unmatched therapy. Larger sample size studies are needed to validate these findings.