Correlation of human epidermal growth factor receptor 2 expression with clinicopathological characteristics and prognosis in gastric cancer

Abstract

Aim: To investigate human epidermal growth factor receptor 2 (HER2) gene amplification and protein expression in Chinese patients with resectable gastric cancer and the association with clinicopathological characteristics and survival.

Methods: One hundred and ninety-seven gastric cancer patients who underwent curative surgery procedures were enrolled into this study. HER2 gene amplification and protein expression were examined using fluorescence in-situ hybridization (FISH) and immunohistochemistry (IHC) analysis on formalin-fixed paraffin-embedded gastric cancer samples from all patients. For scoring, Hofmann's HER2 gastric cancer scoring system was adopted. All cases showing IHC3+ or FISH positivity were defined as HER2 positive. Patient clinicopathological data and survival information were collected. Finally, χ² statistical analysis was performed to analyze the HER2 positivity rate amongst the subgroups with different clinicopathological characteristics including; gender, age, tumor location, Lauren classification, differentiation, TNM staging, depth of invasion, lymph node metastases and distant metastasis. The probability of survival for different subgroups with different clinicopathological characteristics was calculated using the Kaplan-Meier method and survival curves plotted using log rank inspection.

Results: According to Hofmann's HER2 gastric cancer scoring criteria, 31 cases (15.74%) were identified as HER2 gene amplified and 19 cases (9.64%) were scored as strongly positive for HER2 membrane staining (3+), 25 cases (12.69%) were moderately positive (2+) and 153 cases (77.66%) were HER2 negative (0/1+). The concordance rate between IHC and FISH analyses was 88.83% (175/197). Thirty-six cases were defined as positive for HER2 gene amplification and/or protein expression, with 24 of these cases being eligible for Herceptin treatment according to United States recommendations, and 29 of these cases eligible according to EU recommendations. Highly consistent results were detected between IHC3+, IHC0/1 and FISH (73.68% and 95.42%), but low consistency was observed between IHC2+ and FISH (40.00%). The positivity rates in intestinal type and well-differentiated gastric cancer were higher than those in diffuse/mixed type and poorly-differentiated gastric cancer respectively (28.57% vs 13.43%, P = 0.0103; 37.25% vs 11.64%, P < 0.0001), but were not correlated with gender, age, tumor location or TNM stage, depth of invasion, lymph node metastases and distant metastasis. In poorly-differentiated gastric cancer patients, those without lymph node metastasis showed a higher HER2 positivity rate than those with lymph node metastasis (26.47% vs 7.14%, P = 0.0021). This association was not present in those patients with well-differentiated gastric cancer (28.57% vs 43.33%, P = 0.2832). Within our patient cohort, 26 cases were lost to follow-up. The median survival time for the remaining 171 patients was 18 mo. The median survival times of the HER2 positive and negative groups were 17 and 18.5 mo respectively. Overall survival was not significantly different between HER2-positive and negative groups (χ(2) = 0.9157, P = 0.3386), but in patients presenting well-differentiated tumors, the overall survival of the HER2-positive group was significantly worse than that of the HER2-negative group (P = 0.0123). In contrast, patients with poorly differentiated and diffuse/mixed subtype gastric cancers showed no significant differences in overall survival associated with HER2. Furthermore, the median survival time of the HER2 positive group did not show any statistically significant differences when compared to the subgroups of gender, age, tumor location, TNM classification, lymph node metastases and distant metastasis.

Conclusion: Patients with intestinal type gastric cancer (GC), well-differentiated GC and poorly-differentiated GC without lymph node metastasis, may all represent suitable candidates for targeted therapy using Herceptin.

Keywords: Clinicopathological characteristics; Gastric cancer; Gene amplification; Human epidermal growth factor receptor 2; Protein expression.

Figure 1

Fluorescent in-situ hybridization analysis of human epidermal growth factor receptor 2 gene amplification (× 600). A: Normal human epidermal growth factor receptor 2 (HER2) gene expression: Red signals (HER2 gene), green signals [chromosome enumeration probe 17 (CEP17)], blue signals (nuclei lining dye); B: Positive HER2 gene amplification: HER2:CEP17 > 2; C: Positive HER2 gene amplification: HER2:CEP17 > 2 with clear red cluster signals observed.

Figure 2

Immunohistochemical analysis of human epidermal growth factor receptor 2 protein expression (× 200). A: Immunohistochemical (IHC) 0: No staining on tumor cell membrane; B: IHC1+: Faintly perceptible staining on > 10% tumor cell membrane; C: IHC2+: Moderate staining on > 10% tumor cell membrane; IHC3+: Strong staining on > 10% tumor cell membrane.

Figure 3

Kaplan-Meier survival analysis. A: Overall survival curves of 171 gastric cancer patients according to human epidermal growth factor receptor 2 (HER2) detection (P = 0.3386); B: Survival curve of patients with well differentiated gastric cancer according to HER2 expression (P = 0.0123); C: Survival curve of patients with poorly differentiated gastric cancer according to HER2 expression (P = 0.0988); D: Survival curve of patients with the diffuse/mixed type gastric cancer according to HER2 expression (P = 0.6623).