Differences in colorectal cancer patterns between right and left sided colorectal cancer lesions

Colorectal carcinomas that arise proximal (right) or distal (left) to the splenic flexure exhibit different clinical and biological characteristics. Although various hypotheses have been proposed to explain these differences, their origin remains unclear. In this study we investigated the clinicopathologic differences between left and right colon tumors and comment on the possible explanatory theories behind them.

This study included a total of 388 retrospectively collected cases of colorectal cancer, surgically treated from 1999 to 2004. Differences of patients' demographic data and tumor micro- and macroscopic characteristics between left and right-sided tumors were investigated and analysed.

Patients with right-sided colon cancer were significantly older (mean age 70 vs. 68 years; p<0.05) and had more lymph nodes examined than patients with left colon tumors (mean number of nodes 18.9 vs. 12.6; p<0.05). There was a lower proportion of T1 stage right-sided tumors (3.1 vs. 5%) and a higher proportion of stage T2-4 (96.9 vs. 95%) compared with left-sided tumors (p<0.001 for x2 test of all T stages). Furthermore, right-sided tumors had a higher mean width and depth (4.3 vs. 3.8 cm and 1.8 vs. 1.6 cm, respectively; p<0.05). Finally, there was a higher percentage of poorly differentiated right colon tumors (41.4 vs. 17.5%; p<0.001).

Right-sided colon tumors affect older patients and are diagnosed at more advanced disease stages. The underlying mechanisms that provoke these differences remain unclear. Further studies are needed in order to better understand the true nature of these differences and their possible clinical implications.