The stage of the disease and presence of metastasis highly affects the survival rates among the patient group. Most of the CRC cases occurred in the developed regions of the world the highest mortality rates were observed in Central and Eastern Europe, which was 20 per 100,000 men and 12 per 100,000 women. In 2012, about 1.3 million people (746,000 men, 614,000 women) were diagnosed with CRC. For the development of effective therapy regimes and better treatment options, it is essential to evaluate right-sided and left-sided tumors as separate entities, and design the therapy regime considering the differences between these tumors.Īccording to World Health Organization, colorectal cancer (CRC) is the third most common cancer in the world. Right-sided colorectal cancer (RCRC) patients do not respond well to conventional chemotherapies, but demonstrate more promising results with immunotherapies because these tumors have high antigenic load. Left-sided colorectal cancer (LCRC) patients benefit more from adjuvant chemotherapies such as 5-fluorouracil (5-FU)-based regimes, and targeted therapies such as anti- epidermal growth factor receptor (EGFR) therapy, and have a better prognosis. Therapy responses are totally different between these tumor entities. In the left-sided tumors, chromosomal instability pathway-related mutations, such as KRAS, APC, PIK3CA, p53 mutations are observed and these tumors demonstrate polypoid-like morphology. In the right-sided tumors, mutations in the DNA mismatch repair pathway are commonly observed and these tumors generally have a flat histology.
Tumors in the proximal colon (right side) and distal colon (left side) exhibit different molecular characteristics and histology. However, colorectal cancer is not a single type of tumor its pathogenesis depends on the anatomical location of the tumor and differs between right side and left side of the colon. Colorectal cancer is the third most common cancer worldwide with a high mortality rate at the advanced stages.