The treatment of colorectal cancer (CRC) is evolving continuously and many important advances have recently led to improved prognosis. Surgery remains an integral component of multidisciplinary treatment. Targeted therapies are being developed in the laboratory and implemented clinically, thus taking advantage of major advances in understanding the molecular biology of CRC. This chapter briefly reviews the epidemiology of CRC and then the molecular biology of CRC and discusses inherited CRC syndromes, and also CRC screening and surveillance.
Colorectal cancer is the third most common cancer in the United States in both men and women and the third most common cause of cancer-related death in the United States, accounting for more than 50,000 deaths annually.1 Worldwide, CRC affects over a million people and the incidence appears to be increasing globally.2 In the United States, the incidence of CRC is declining, possibly as the result of improved screening and early detection. However, the risk of developing CRC remains approximately 1 in 21 for women and 1 in 19 for men.1 The average age of diagnosis is 72 years.3 Age is a strong risk factor for CRC and the vast majority of cases occur in patients over 50 years of age.1,4,5 The probability of developing CRC for a patient less than 40 is less than 1 in 1000, but increases to approximately 1 in 25 for patients 70 years or older. Interestingly, though the incidence of CRC is decreasing for the U.S. population in general, it appears to be slightly increasing in younger patients.6 African Americans develop CRC with increased frequency compared to Caucasians, a fact which is relevant to newer screening guidelines.
In general survival for CRC is better compared to other GI malignancies. Five-year survival for patients presenting with all stages of CRC is 64%.1 Survival is clearly influenced by the stage of disease at presentation. Five-year survival for patients with localized CRC is approximately 90%, compared to 69% for regional disease and 12% for all patients with metastatic disease.7 This underscores the importance of early diagnosis. When appropriately diagnosed, CRC is a survivable disease. There are over 1 million CRC survivors alive in the United States.8
POLYPS AND DEVELOPMENT OF CARCINOMA
Polyps are localized projections of mucosa above the level of the surrounding tissue.5,9 Polyps can be broadly classified according to malignant potential. Benign polyps include hyperplastic, hamartomatous, and inflammatory. Polyps with neoplastic potential include adenomatous, serrated, and hamartomatous polyps (Table 106-1). Adenomatous polyps are the most common, representing about 65% to 75% of identified polyps.5,10 These polyps can be further classified based on histology as tubular, tubulovillous, or villous.
Classification of Polypsa