Rectal carcinoma represents 35-40% of colorectal cancers . Colorectal carcinoma is one of the most common tumours in developed countries and is the third in terms of frequency. It is the second most common cause of death from neoplasia. In Italy around 20 000-30 000 new cases of rectal cancer are observed each year. The 5-year survival rates are around 50-60%, depending on the stage of the disease. Rectal carcinoma has a very good prognosis when confined to the wall of the rectum, while poor prognosis is associated with extension beyond the wall and lymph node metastasis . Patients with residual tumour (R) have poor survival rates; patients with microscopic residual tumour (R1) have a slightly better prognosis than those with macroscopic residual tumour (R2). R1 patients are generally associated with locoregional disease while R2 patients have distant metastases .
The outcome depends essentially on early diagnosis. Colorectal carcinoma arises, in the majority of cases, from macroscopically assessable precancerous lesions, namely adenomatous polyps . Genetic studies have characterised the molecular basis of the adenoma-carcinoma sequence.
About 75% of new cases of colorectal carcinoma are observed in patients with no obvious risk factors, while 25% of patients are associated with high-risk categories. The latter include hereditary conditions (up to 5% of colorectal carcinomas) such as familial adenomatous polyposis coli (FAP) and hereditary non-polyposis colorectal cancer (HNPCC).
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