Expression of HER-2 in rectal cancers treated with preoperative radiotherapy: a potential biomarker predictive of metastasis.

BACKGROUND: Evidence suggests HER-2 overexpression may be predictive of prognosis in colorectal cancer patients, though this remains controversial.
OBJECTIVES: This study was performed to assess the prognostic value of HER-2 expression in locally advanced rectal cancer patients after preoperative radiotherapy. PATIENTS AND METHODS: HER-2 expression was evaluated based on immunohistochemical (IHC) staining of resected specimens from 142 mid-to-low rectal cancer patients. Fluorescence in situ hybridization (FISH) was performed to confirm HER-2 overexpression in samples with an IHC score of 2+. Tumor regression grading (TRG) of the primary tumors was determined semiquantitatively using a tumor regression grading scheme advocated in the AJCC Cancer Staging Manual 7 edition.
RESULTS: When the total staining intensity was evaluated, 106 samples (74.6%) showed barely-perceptible positivity (0-1+; HER-2--negative), 15 samples (10.6%) showed moderate positivity (2+) and 21 samples (14.8%) showed strong positivity (3+, HER-2 positive). FISH confirmed that 2 cases showing moderate HER-2 positivity (2+) overexpressed HER2. There was no significant difference between the HER-2 positive and -negative groups with respect to age, gender, TRG, TNM stage, downstaging status, lymphovascular invasion or tumor differentiation. A significant correlation was found between HER-2 overexpression and the incidence of distant metastasis (p = 0.005). Subgroup analysis revealed this correlation was not significant (p = 0.247) in the radiation-insensitive (TRG0-2) subgroup, whereas a significant correlation (p = 0.026) between HER-2 overexpression and distant metastasis was found in the radiation-resistant (TRG3) subgroup. Multivariate analysis identified ypN stage (OR = 0.473, p = 0.002)and overexpression of HER-2 (OR = 3.704, p = 0.008) as independent risk factors for distant metastasis. There was no correlation between HER-2 overexpression and disease-free survival or overall survival among the study population. LIMITATIONS: We reported that HER-2 overexpression was correlated with distant metastasis in rectal cancer patients, especially in the radiation-insensitive group. However, there are certain limitations. First, this study was limited due to the fact that the number of rectal patients enrolled was only 142, which is relatively small. Second, HER-2 expression was measured by IHC with a positive ratio around 15%, which is fairly high according to the literature. Also, we collected the tissue samples preoperatively. It would be interesting to know the HER-2 expression levels pre- and postradiotherapy, as well as their correlation with local recurrence or distant metastasis. Finally, in rectal cancer patients, there is little information published on HER-2 and its role in tumor progression and metastasis. Therefore, we are pursuing the regulatory molecule underlined.
CONCLUSIONS: HER-2 is overexpressed in around 15% of rectal cancer patients who receive neoadjuvant radiotherapy. Moreover, HER-2 overexpression could be a predictive biomarker of distant metastasis in rectal cancer patients after preoperative radiotherapy, especially patients showing a poor response to neoadjuvant radiotherapy.