Rightward shift in colorectal cancer: experience in 1101 patients.

Background: In the past decades the right colon cancer showed a higher incidence rate than left colon cancer. This trend is known as "proximal shift" or "rightwards shift." We evaluated rightward shift phenomenon in our region.

Methods: We collected data from 1101 colorectal cancer patients who underwent curative surgery at Parma University Hospital from 01 January 2004 through 01 January 2018. We divided patients into seven subgroups according to the time of surgery to evaluate epidemiological changes through the years of colon cancer.

Results: We found a non-linear rightward shift trend of CRC. The incidence of RCC was the 40% between 2004-2005 and 51% in the biennium 2016-2017 (60% in 2012-2013 and 57% in 2014-2015). The patients with RCC were significantly older than patients with LCC. RCCs have poor differentiated tumors. Metastatic disease showed a similar distribution both in left and right CRCs. Peritoneum was the most common metastasis location from right-sided colon cancer.

Conclusions: Data suggest the existence of two different tumor entities in CRC between right-sided colon cancer and left-sided colon cancer. The proximal shift may be a reflection of improved screening programs, diagnostic accuracy and population aging. Ethnicity, gender, diet, environment, and socioeconomic status contribute to CRC incidence and prevalence in different regions.