Risk factors

Certain factors may increase your risk:

  • 50 years old or older
  • Family history of colon cancer
  • Certain genetic alterations
  • A diet rich in fat and red meat
  • Heavy alcohol use
  • Smoking
  • Diabetes, obesity, and lack of exercise

Kari Syrjänen, MD, PhD, FIAC, Chief Medical Director, Biohit Oyj

Cancer of the colon and rectum (colorectal cancer) continues to be one of the leading causes of cancer morbidity and mortality worldwide, more than 1.2 million new cases and 609.000 annual deaths (1). The majority of Colorectal cancer (CRC) cases are classified as sporadic, and 75% of them are estimated to develop in people who are considered to be at moderate risk of developing this disease. Only about 20% of CRC cases are found among people known to be have some degree of family history. The remaining 80% occur in patients with a predisposing inflammatory bowel disease (ulcerative colitis), or any of the known gene mutations (FAP, familial adenomatous polyposis, or HNPCC, hereditary, non-polyposis colorectal cancer)(2,3). Already the early case-control studies showed that the risk of developing CRC is more than double among the subjects with their first-degree relatives having the same disease (4).

It is currently estimated that at least 95% of all CRC cases develop from clearly identifiable precursors, such adenomatous polyps and flat adenomas (5). This progressive adenoma-to-cancer pathogenesis is based on extensive population studies, according to which the bowel cancer risk is many times higher in people who suffer from hereditary polyposis syndromes, as well as on follow-up studies, indicating that the development of CRC was reduced by 60 to 90% among individuals who had undergone an endoscopic removal of their polyps (polypectomy)(6).  Well-designed case-control studies also show conclusively that the removal of polyps in sigmoideoscopy resulted in reduction of CRC mortality by more than 60% during 10 years of follow-up, as compared to the respective control subjects (7).

In their microscopic structure, adenomas are benign tumors, which, however, are considered as CRC precursors, due to the reasons described above. On the basis of their microscopic structure, three main types of adenoma are distinguished: tubular, tubulo-villous and villous adenoma, listed in the order of their increasing tendency for malignant transformation.  Adenomas are accompanied by precancerous lesions of different degree of severity, known as dysplastic changes, of which the most severe forms represent local cancer (carcinoma in situ, CIS). Only when the malignant tissue grows through the mucosal muscle layer, it is referred to as an invasive adenocarcinoma.


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