Expression of HER2 and PDL-1 in colorectal carcinoma-single center analysis

Colorectal cancer as an aggressive malignant neoplasm by incidence has the third place in men after lung
and prostate cancer, and the second place in woman after breast cancer. There are near 600.000 deaths every year
worldwide associated with colorectal carcinoma. Due to tumor heterogeneity and molecular profile new therapeutic
strategies and trials are emerging. HER2, which is more commonly used as a biomarker in breast cancer and gastric
cancer, in the last decade has been investigated as potential target treatment in colorectal cancer. After the benefit from anti PD-1 monoclonal antibodies in non-small cell lung carcinoma, melanoma and renal cancer, new clinical
trials are evaluating PDL-1 expression and its scoring systems. Our aim in this retrospective-prospective study is to evaluate the immunohistochemical expression of HER2 and PDL-1 and explore the case characteristics. We analyzed 90 cases of metastatic colorectal carcinoma diagnosed at Clinical Hospital Acibadem-Sistina on a tissue
microarray with HER2 clone 4B5 and PDL-1 clone SP263. In the HER2 positive group mostly were male patients (72.22%) and patients over 50 years of age (91.67%). Moderately differentiated were mostly HER2-positive tumours with scores of 2+ (78.13% ) and 3+(75%). The majority of HER2-positive tumors were localized in the left colon, regardless of the intensity of expression. 12 out of 30 K-RAS/N-RAS positive cases showed HER2 expression, 5 of 9 BRAF positive cases showed HER2 expression and 3 of 5 MMRd cases showed HER2
expression. Male patients were represented by 58.82% and females by 41.18% in the PDL1 positive expression.
PDL1 positive tumors with cut off more than 1% were in 70% and cut off more than 10% in 75% of cases were most commonly moderately differentiated and with more than 50% positive tumor cells were most commonly poorly differentiated (66.67%). All 3 cases with more than 50% positive tumor cells were localized in right colon.
Four of 26 K-RAS/ N-RAS positive cases showed expression for PDL-1, 3 of 6 BRAF positive cases showed expression for PDL-1 and 2 of 3 MMRd cases showed expression for PDL1.Molecular profiling is mandatory in the treatment of colorectal carcinoma. The official recommendations are to test HER2 expression in all cases with advanced metastatic disease of colorectal carcinoma. PDL-1 in recent years has become a potential target for cancer therapy. Although the role in colorectal cancer is less clear, overexpression of PDL1 is linked with worse prognosis, BRAF mutations and right sided location.