Investigation of targetable predictive and prognostic markers in gallbladder carcinoma

Gallbladder carcinoma, uncommon in most of the world, is frequent in South East Asia. It presents in advanced stages with limited therapeutic options. We investigated targetable predictive and prognostic Markers in 268 cases including 233 primary site lesions and 35 metastatic gallbladder carcinoma.

EGFR, VEGF, HER2/Neu and p53 were assessed using immunohistochemistry. HER2/Neu was validated in a subset by fluorescent in situ hybridization (FISH) using tissue microarray (TMA). Broader spectrum of gene variation was screened in NGS in representative FFPE tissue using the Ion AmpliSeq cancer hotspot panel V2.

Mean age was 49.5 years with female predominance (77.6%). Histological types included 221 cases of adenocarcinoma not otherwise specified (NOS), 23 invasive papillary carcinoma, 11 mucinous adenocarcinoma, 8 adenosquamous, 1 signet ring, 3 neuroendocrine and 1 undifferentiated carcinoma. Majority (76.1%) presented with stage 3/4 disease. Overall positive expression of p53 was 44.8%, VEGF 79.4%, HER2/Neu 27.3% and EGFR 34.6%. Intratumoral heterogeneity was evident in HER2/Neu. Marker expression was not significantly associated with stage, grade, type and metastasis except VEGF which correlated with histological type (P=0.018) and tumor grade (P=0.027). NGS using Ion AmpliSeq cancer hotspot panel V2 revealed multiple non synonymous mutations, most frequent being TP53 and CDKN2A mutations and mutations in MET, KDR, PIK3CA, VHL, MPL, HER2 and SMARCB1 genes.

Predictive targetable markers like HER2/Neu, VEGF and EGFR are expressed in high proportion of gallbladder carcinoma. Significant expression of RAS pathway molecules suggests that interactions take place among the different members of the ErbB family during tumor development.