Abstract

BackgroundGastric cancer is one of the deadliest cancer entities worldwide. While surgery is the only curative treatment option in early tumors, for locally advanced and metastatic patients further therapeutic targets are needed. Several studies not only reported mutations but also amplifications of the KRAS locus in different cancer entities. More recently, KRAS amplification was discussed as a new therapeutic target. Little is known about the (prognostic) relevance and (heterogenic) distribution of KRAS amplification in gastric adenocarcinomas, especially in Non-Asian patients.MethodsAmplification of the KRAS locus and corresponding protein expression was analyzed in 582 gastric adenocarcinomas employing fluorescence in-situ hybridization (FISH) and immunohistochemistry. Amplification status was correlated with clinico-pathological features, clinical outcome and molecular tumor data including a correlation to the TCGA subtypes of gastric carcinoma.ResultsKRAS amplification was detected in 27 out of 470 analysable tumors (5.7%) and correlated with protein expression of KRAS in all amplified tumors. Within the KRAS amplified gastric tumors 14/27 (51.9%) showed a heterogeneous distribution with also KRAS non-amplified tumor parts. According to TCGA 24 tumors (88.8%) were related to chromosomal instable tumors (CIN). The survival analysis of the entire patient cohort did not show any difference in overall survival in dependence on the KRAS status. However, a significant survival difference with a worse outcome for patients with KRAS amplified tumors was identified when analysing patients without neoadjuvant pre-treatment.ConclusionsWe confirm the unfavorable prognosis of KRAS amplified tumors reported by other studies in (Asian) patient groups, at least in patients without neoadjuvant pre-treatment. Within KRAS amplified tumors we revealed intratumoral heterogeneity that may define a (more aggressive) tumor cell population which is more frequently observed in patients with lymph node metastases. Despite the heterogeneous distribution of KRAS amplified tumor clones, KRAS amplified locally advanced or metastasized gastric adenocarcinomas represent a therapeutically highly relevant tumor subgroup.

Highlights

  • Gastric cancer is one of the deadliest cancer entities worldwide

  • Clinico-pathological and patient characteristics The entire patient cohort consisting of 582 patients with gastric adenocarcinoma were considered for analysis

  • Kirsten rat sarcoma viral oncogene (KRAS) amplification KRAS amplifications were observed in 27 patients (5.7%)

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Summary

Introduction

While surgery is the only curative treatment option in early tumors, for locally advanced and metastatic patients further therapeutic targets are needed. Several studies reported mutations and amplifications of the KRAS locus in different cancer entities. KRAS amplification was discussed as a new therapeutic target. Little is known about the (prognostic) relevance and (heterogenic) distribution of KRAS amplification in gastric adenocarcinomas, especially in Non-Asian patients. Among sporadic (distal) gastric adenocarcinomas Helicobacter pylori infection remains the most important cause which can partly reflect the different incidence rates worldwide [3, 4]. The ToGa (Trastuzumab for Gastric Cancer) trial demonstrated improved overall survival in patients with Her2/neu amplified tumors who received trastuzumab in addition to standard chemotherapy in comparison to chemotherapy alone [6]. Heterogeneity of gene amplifications within primary gastric adenocarcinomas is not uncommon

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