Molecular profiling-guided therapy in gastroesophageal carcinoma: A single-institution experience.

Abstract

e15582 Background: Gastroesophageal carcinoma (GEC) including carcinoma of stomach (GC), gastroesophageal junction (GEJ), and esophagus (EC) is the 2nd leading cause of cancer death worldwide. Chemotherapy and HER2-targeted therapy (trastuzumab) have shown limited efficacy. We aim to assess the impact of molecular profile (MP)-guided therapy (MPgt) by correlating expression of select biomarkers in GEC patients (pts) with survival. Methods: 27 GEC (11 GC, 9 GEJ, 7 EC) submitted to Caris Life Sciences for molecular profiling between 2011 and 2016 were analyzed and correlated with pt survival. The impact of MPgt was assessed by calculating the ratio of progression-free survival (PFS) on MPgt to PFS on the preceding empiric therapy. MPgt was deemed beneficial if PFS ratio ≥1.3. Results: In-situ hybridization indicated amplification of HER2 (15.4%) and c-MET (7.4%). Immunohistochemistry revealed increased expression of TOPO1 (57.7%), TOP2A (38.5%), HER2 (15.4%) and c-MET (6.9%), as well as decreased expression of TS (69.2%), ERCC1 (42.3%), and PGP (15.4%). These data suggest sensitivity to topoisomerase inhibitors, anthracyclines, trastuzumab, MET-targeted therapy, fluoropyrimidine, platinums, and taxanes, respectively. Expression of these markers was heterogeneous among pts, and a trend toward improved PFS was noted in pts with low/absent ERCC1 expression on platinum-based therapy ( P= 0.06). Of the 13 pts who had sufficient data to assess the benefit of MPgt, 5 (38%) achieved a PFS ratio ≥1.3. One pt with metastatic HER2-amplified EC who had initially demonstrated clinical benefit from trastuzumab-containing chemotherapy, developed a new HER2 and c-MET co-amplified lung metastasis. Conclusions: While MPgt was beneficial in 38% of pts, tumor-associated plasticity, clonal evolution, and adaptive resistance may have limited efficacy. The emergence of HER2 and c-MET co-amplified clones is a potential resistance mechanism in HER2-amplified GEC, and highlights combined inhibition of receptor tyrosine kinases as a therapeutic strategy. Further studies with expanded data sets will be needed to test the hypothesis that actionable targets can be used independently to predict treatment response in GEC pts.