Variability in HER2 expression between primary colorectal cancer and corresponding metastases.

PURPOSE: This study aimed to investigate the HER2 status of primary colorectal cancer (CRC) and corresponding metastases, and determine the correlation between HER2 and clinicopathological characteristics.

METHODS: We collected the clinicopathological features of 98 CRC patients and 66 patients which were previously evaluated for the KRAS status. The tissue samples of primary CRC tumors (n = 98), noninvolved colorectal mucosa (n = 98), paired lymph nodes (n = 98, 69 patients had positive metastatic nodes), and liver metastases (n = 22) were evaluated using immunohistochemistry for HER2. The kappa test was used to evaluate the concordance rate of HER2 status. Survival analysis was established according to the Kaplan-Meier method.

RESULTS: HER2 overexpression was more common in primary tumors among the younger patients (P < 0.05). No survival significance was revealed in the HER2 status. The HER2-positive rate was 11.2% for the primary CRC tumors, 0% for the normal adjacent mucosa tissues, 10.1% for the matched positive lymph nodes, and 31.8% for the corresponding metastasis. Seven of sixty-nine cases (10.1%) exhibited biomarker discordance in nodal metastases compared with primary tumors (κ = 0.48, P < 0.05); 6 out of 22 cases (27.3%) exhibited biomarker discrepancy in liver metastases compared with primary tumors (κ = 0.32, P > 0.05). Compared with lymph nodes, HER2 overexpression in the primary tissue was more common in KRAS wild-type patients (P < 0.05).

CONCLUSIONS: The present study showed a high rate of discordance in matched pairs of primary tumors and metastases, suggesting that the accurate evaluation of HER2 status is essential before any therapeutic decision.