Expression of Trop2, Nectin-4, and FOLR1 cell surface markers in biliary tract cancers: Is it time to repurpose drugs?

Abstract

637 Background: Biliary tract cancers (BTC), including gall bladder cancer, intrahepatic and extrahepatic cholangiocarcinoma are aggressive malignancies, with poor prognosis. Despite advances in frontline setting, and in biomarker selected population (IDH1, FGFR2, Her2, BRAF, HRD), there is a dire need to advance therapy in subsequent lines. Methods: We identified BTC patients (pts) at Roswell Park Cancer Center who underwent curative intent surgery between 01/2006-01/2020. After excluding duplicate samples and those with insufficient tissue, we found 78 pts with adequate follow up for analysis. Expression of trophoblast cell surface antigen 2 (Trop2), nectin4, folate receptor alpha (FOLR1) was assessed by immunohistochemistry and correlated with clinical outcomes. H score, a weighted index score that factor in, the % of cells across different intensity was calculated. H scores were classified as negative (0) and positive (>1). Positive H scores were grouped as weak (1-100), intermediate (101-200) and strong (201-300). Descriptive statistics were conducted, and multivariate analyses performed (R studio) to study any correlation between expression of markers and survival outcomes. Results: The median age of our cohort was 67.5 years (range 40-87) with 58% male; 24.4%, 30.8%, 20.5%, 7.7% had stages I, II, III, IV disease. Staging information was missing in 16.7% of pts. Of 73 analyzable samples for Trop2, all were positive for Trop2, with a mean H score of 86, SD of 68.9. 56.4% of patients had a weak H score, 30.8% had an intermediate H score and 6.4% had a strong H score for Trop2. Median overall survival (mOS) among low, intermediate and high expressing group of pts with Trop2 was 48.9 months (m), 23.9 m, and 41.9 m with median Progression Free Survival (mPFS) of 37.8m, 15.3 m, and 37.4 m, respectively. Of 75 analyzable samples for FOLR1 and Nectin4, FOLR1 was expressed in 51.3% with a mean H score of 6.97 (SD 21.9). Nectin4 was expressed in 78.2%, with a mean H score of 13.7 (SD 26.3). Pts with Trop2 expression had a mOS of 39.5 m and a mPFS of 28.7 m. There were no significant differences in mOS (48.9 m vs 33.3 m, p =0.14) and mPFS (37.8 m vs 26.2 m, p =0.35) among patients with positive vs negative FOLR1 respectively. There was no difference in mOS (41.6 m vs 38.3 m, p=0.92) and mPFS (32.8 vs 26.4 m, p-value=0.5) in patients with positive vs negative Nectin4. Multivariate analyses showed that pts with intermediate Trop2 (H score=101-200) had a high risk of death (HR 21.44, CI 2.81-163.4, p= 0.003). Conclusions: Though no difference was seen in clinical outcomes in pts with strong Trop2 expression, FOLR1, and Nectin4 expression, this could be explained by the small sample size. Trop2 is frequently expressed in BTCs and patients with Intermediate Trop2 H score had lower mOS and mPFS, with a higher risk of mortality. This warrants further investigation into potential use of Antibody Drug conjugates against Trop2 in BTC.