Clinical and molecular characteristics of advanced esophageal/GEJ cancer with brain metastasis.

Abstract

e16092 Background: Brain metastasis (BRM) in gastroesophageal (GE) cancer is uncommon, but contributes to poor prognosis and significant symptom burden. While HER2 overexpression has been suggested as a potential driver of BRM, clinicopathologic and molecular determinants of BRM in GE cancer and their impact on clinical outcome remain incompletely understood. Methods: We retrospectively analyzed clinicopathologic data from 323 advanced esophageal/GEJ patients (pts) at Johns Hopkins from 2003 to 2021. Univariate and multivariate logistic regression were performed to investigate the association between several clinical and molecular features and the occurrence of BRM, with particular focus on HER2 overexpression (by IHC and FISH) and PD-L1 expression (by IHC) as measured by the combined positive score (CPS). Overall survival was estimated using the Kaplan-Meier method. Results: Median age was 64 and most pts were white (90.4%). Tumors were 73.7% esophageal primary, 82.7% adenocarcinoma, 43.8% HER2+, and 11.1% CPS ≥ 1. Cumulative incidence of BRM in overall cohort and within HER2+ subgroup was 14.6% (47 pts) and 25.4% (16 pts), respectively. Pts with BRM (not already present at time of stage IV diagnosis) had median onset of 10.8 months. Seventeen (36.2%) pts had a solitary brain lesion and 10 (21.7%) were asymptomatic. On univariate analysis, adenocarcinoma and HER2 overexpression were associated with increased risk of BRM (OR 3.45; 95% CI 0.09-0.96; p = 0.043 and OR 2.72; 95% CI 1.11-6.67; p = 0.028, respectively). Notably, the HER2 association was strengthened when HER2 equivocal tumors were re-classified as positive in an exploratory analysis (OR 3.55; 95% CI 1.38-9.14; p = 0.009). Adenocarcinoma and HER2 overexpression were collinear in the multivariate model. In pts with BRM, OS was improved in HER2+ pts (16.72 months; 95% CI 12.3-21.1 months; log-rank p = 0.039 and OR 0.33; 95% CI 0.11-0.99; Cox regression p = 0.049). CPS and primary tumor location were not associated with increased BRM. Conclusions: HER2 overexpression identifies an esophageal/GEJ molecular subtype that is significantly associated with increased risk of BRM; though with improved OS (compared to non-HER2+ BRM) and later onset CNS progression, likely reflecting durable extra-CNS control on targeted systemic therapy and a potential HER2+ subgroup with relatively indolent biology. Prevalence of asymptomatic and solitary brain lesions supports increased brain surveillance for this population.