Right- and Left-Sided Colonic Cancer - Different Tumour Entities?

Purpose: Colorectal cancer is one of the most common malignancies in the Western world. In the past two decades, a growing amount of data has been reported suggesting that carcinomas of the right and left colon should be considered as different tumour entities. The aim of this review is to present a detailed analysis of the current knowledge regarding differences between right- and left-sided colon cancer and potential consequences for daily practice. Methods: For this report all articles with relevant information on differences between right- and left-sided colon carcinoma found via Pubmed searches were analysed. Furthermore, findings of a previous study performed by our group were included. Results: Patients with right- sided colon cancer are significantly older, predominantly women, with a higher rate of comorbidities. Most of the large epidemiological studies reported a continued rightward shift of colorectal cancer. Histopathologically, carcinoma of the right colon show a higher percentage of poorly differentiated, locally advanced tumours with a higher rate of mucinous carcinoma and different pattern of metastatic spread. Survival is significantly worse in patients with right- sided carcinomas. There are numerous genetic differences which account for the distinct carcinogenesis and biological behaviour. Conclusions: The numerous findings regarding differences between right- and left-sided colon cancers should have an impact on colon cancer screening and therapy. Firstly, there are defined risk groups which should receive complete colonoscopy, particularly if they present with symptoms suspicious for colon carcinoma. Furthermore, location of the colon cancer should be considered before group stratification into genetic, clinical and especially chemotherapy trials. A more tailored approach to colon cancer treatment would be highly desirable if future trials further support the hypothesis of two distinct tumour entities.