Improving detection of colorectal cancer

Colorectal cancer is the third most common cancer in the U.K., with an annual incidence of 36,100 in England and Wales. It is also the second leading cause of death from cancer in the U.K. However, there has been a significant increase in five-year survival over the past decade, from 22% to 50% despite more than 55% of patients presenting with lymph node or distant metastases. Around 80% of colorectal cancer is sporadic, i.e., caused by the interaction of genetic and environmental factors via the adenoma-carcinoma sequence and cancer may take up to ten years to develop in this way. Adenomas are more common with age and one in four of the population aged over 50 will develop one or more polyps, with 10% of these polyps progressing to cancer over time. Risk factors for colorectal cancer include: age over 60; K-ras and p53 mutations; a diet high in saturated animal fat and low in fibre and vegetables; lack of exercise, obesity and excessive alcohol intake. Inflammatory bowel disease is a risk factor for development of colorectal cancer through the association of chronic inflammation and development of malignancy. Around 20% of colorectal cancer cases are familial and in a primary care setting taking a family history may determine those with a higher than average risk who may need onward referral. A large proportion of patients with rectal or sigmoid cancers present with a combination of rectal bleeding and a change in bowel habit (usually an increased frequency of defecation and/or looser stools). Rectal bleeding in the absence of anal symptoms occurs in over 60% of those with cancer, and a palpable rectal mass with or without tenesmus is present in 40-80% of those with rectal cancer.