Background:In Indonesia, colorectal cancer is the third most common type. In 2008, Indonesia ranked fourth in the Association of Southeast Asian Nations (ASEAN) countries, with an incidence rate of 17.2 per 100 000 population. This figure is predicted to continue to increase from year to year. In 30% of colorectal cancer patients diagnosed after metastases, some patients will develop metastases after undergoing surgical resection of the primary tumor. The survival of metastatic colorectal cancer patients has improved significantly in the last 20 years with the introduction of target-oriented drugs, anti–epidermal growth factor receptor (EGFR), and anti–human epidermal growth factor receptor-2 (HER2). This study aims to assess the relationship between Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation and HER2 expression for targeted therapy implementation.Patients and methods:This research is a cross-sectional study. The research subjects in this study were colorectal cancer patients in the digestive surgery division. There were 58 study subjects. Examination of KRAS mutations was carried out by PCR on fresh tumor tissue obtained from surgery or colonoscopy. Meanwhile, the HER2 examination used the immunohistochemistry method of paraffin blocks for anatomical pathology examination.Results:Examination of KRAS mutations showed 28/58 (43.8%) patients with colorectal cancer, while HER2 overexpression was found in 6/58 (10.3%) patients with colorectal cancer. Univariate analysis of KRAS mutations and HER2 expression showed that four subjects with KRAS mutations had excess HER2 expression (P=0.341).Conclusion:There is no association between KRAS mutations and HER2 overexpression in colorectal cancer patients.