HER2 gene (ERBB2) amplification is a rare event in non-liver-fluke associated cholangiocarcinogenesis

Abstract

Background: Cholangiocarcinoma is a rapidly fatal cancer entity with a median survival of less than one year. In contrast to many other malignancies, no substantial therapeutic breakthrough has been made in the past few decades, thereby limiting the treatment to cytotoxic chemotherapy with little beneficial effect for most patients. Targeted therapy tailored to the individual has shown substantial success in the recent past as a promising avenue for cancer therapy.

Methods: In this study, we determined the frequency of amplification of the HER2 gene in a comprehensive and well-characterized European cholangiocarcinoma cohort encompassing 436 patients including intrahepatic (n = 155), proximal (n = 155) and distal (n = 126) cholangiocarcinoma by strict application of a combined immunohistochemical and in situ hybridization algorithm following the current guidelines for HER2 assessment in gastric cancer.

Results: We identified a proportion of 1.4% (n = 6) patients that demonstrated HER2 gene amplification, with the highest rate among the distal cholangiocarcinoma patients (2.4%). None of the patients with equivocal (2+) immunohistochemical staining results exhibited gene amplification molecularly. In four of the five patients with HER2 positivity, gene amplification was already present in concomitantly tested high-grade biliary intraepithelial neoplasia (80%). HER2 gene amplification was not significantly associated with other clinical parameters, including survival.

Conclusions: This study identifies HER2 gene amplification as a rare event in cholangiocarcinoma of the Western population, occurring already in high-grade BilIN in a subset of patients. Furthermore, we provide a robust testing algorithm that may be used prior to therapy administration in future clinical trials evaluating the role of HER2 as a predictive marker in cholangiocarcinoma.

Keywords: Biliary tract cancer; Cholangiocarcinoma; HER2; Predictive biomarkers; Targeted therapy.

Fig. 1

HER2 scoring algorithm in cholangiocarcinoma. HER2 status was determined using a four-tier immunohistochemical scoring system, complemented by chromogenic in situ hybridization. Negativity was defined by an IHC score of 0 (a) and 1+ (b). Equivocal 2+ IHC staining (c) was not accompanied by gene amplification in chromogenic in situ hybridization (d). Positive 3+ IHC staining (e) was paralleled by gene amplification in all cases, as shown by the accumulation of green over red signals with a ratio ≥ 2.0, including prominent signal clustering in two patients (f). Original magnification A-F [400x]

Fig. 2

HER2 positivity in high-grade biliary intraepithelial neoplasia. All cases with HER2 negativity in the invasive cholangiocarcinoma component also lacked HER2 positivity in concomitant high-grade precursor lesions (biliary intraepithelial neoplasia, grade 3) (a). Four of five cases with available concomitant precursor lesions exhibited HER2 positivity already in biliary intraepithelial neoplasia, grade 3 (b). Note the abrupt change in HER2 staining from non-dysplastic to dysplastic epithelium (arrowhead). Original magnification A-B [400x]

Fig. 3

Survival analysis of CCA patients stratified for HER2 gene amplification Displayed are the survival curves for the HER2-negative patients (red curve) and the HER2-positive patients (blue curve) (n = 361). Median survival was nominally lower in the HER2-negative group (3.8 years) than in the HER2-positive group (6.9 years), though not statistically significant (p = 0.471)