Aspects of colorectal cancer screening, methods, age and gender

Abstract

Colorectal cancer (CRC) is, besides breast, prostate, lung and skin cancers, the most common cancer worldwide and is suitable for screening. The incidence of CRC varies considerably in different parts of the world: in well-developed countries, the incidence is between 30 and 70 per 100 000 inhabitants, whereas in less-developed countries such as sub-Saharan Africa, it is 10-20/100 000 inhabitants. Women have a lower incidence of CRC, which is usually one-third of total incidence. Several studies have shown that it is possible to decrease mortality from CRC with about 20%, which is evidenced through the data from countries with screening programmes. Though the method of choice to identify blood samples in faecal matter is under debate, the most feasible way is to perform colonoscopy. Other methods include more advanced faecal analyses, testing for mutations from CRC, sigmoidoscopy, CT colonoscopy or optical colonoscopy. Colonoscopy is in most countries not available in sufficient amount and has to be carried out with great accuracy; otherwise, lesions will be missed to identify, thus leading to complications. Gender is an issue in CRC screening, as women have about 20% fewer colorectal adenomas and CRCs, but they also have more right-sided lesions, which are more difficult to detect with tests for faecal blood since they create less blood in faeces. Thus, other strategies may have to be developed for women in order for screening to have the same effect. It is essential to introduce colorectal cancer screening in all countries together with other clinical pieces of advice such as information on smoking, obesity and exercise in order to reduce one of the most dangerous cancers.

Keywords: F-Hb; colonoscopy; colorectal cancer; screening.

Fig. 1

Distribution of the different stages for CRC at the time of diagnosis.

Fig. 2

The incidence of CRC in different parts of the world (from WHO GLOBOCAN https://gco.iarc.fr/).

Fig. 3

Three different stages in the adenoma carcinoma sequence. (The figures are shown with courtesy of Stefan Willmarsson) (a) Traditional big adenomatous polyp with a prominent stalk. (b) A sessile serrated polyp. (c) Colorectal cancer with ulceration.

Fig. 4

Computerized tomography of a small polyp in a so‐called fly‐through image (Courtesy: Mikael Hellström).

Fig. 5

Most important sex differences between men and women. Right‐sided tumours are more common in women and patients with HNPCC and seem to be correlated with high intake of carbohydrates and fat, and they have more microsatellite instability and BRAF mutations. Left‐sided lesions are more common in men and patients with FAP, and they are correlated with high intake of protein (meat) and calcium and have more APC, KRAS and P53 mutations.