Incidence and mortality
Colorectal cancer (CRC) is the third most common malignant neoplasm worldwide  and the second leading cause of cancer deaths (irrespective of gender) in the United States. It is estimated that there will be 142,820 new cases diagnosed in the United States in 2013 and 50,830 deaths due to this disease. Between 2005 and 2009, CRC incidence rates in the United States declined by 4.1% per year among adults aged 50 years and older. For the past 20 years, the mortality rate has been declining in both men and women. Between 2005 and 2009, the mortality rate declined by 2.4% per year in men and by 3.1% per year in women. In adults younger than 50 years, CRC incidence rates increased by about 1.1% per year. The overall 5-year survival rate is 64%. About 5% of Americans are expected to develop the disease within their lifetimes.[2,3] The risk of CRC begins to increase after the age of 40 years and rises sharply at ages 50 to 55 years; the risk doubles with each succeeding decade, and continues to rise exponentially. Despite advances in surgical techniques and adjuvant therapy, there has been only a modest improvement in survival for patients who present with advanced neoplasms.[4,5] Hence, effective primary and secondary preventive approaches must be developed to reduce the morbidity and mortality from CRC.
Definition of prevention
Primary prevention involves the use of medications or other interventions before the clinical appearance of CRC with the intent of preventing clinical CRC and CRC mortality.
Etiology and pathogenesis of colorectal cancer
Genetics,[6,7] experimental,[8,9] and epidemiologic [10,11,12] studies suggest that CRC results from complex interactions between inherited susceptibility and environmental factors. The exact nature and contribution of these factors to CRC incidence and mortality is the subject of ongoing research.
Factors associated with increased risk of colorectal cancer
Excessive alcohol use
There is evidence of an association of CRC with alcoholic beverage consumption. In a meta-analysis of eight cohort studies, the relative risk (RR) for consumption of 45 g/day (i.e., about three standard drinks/day) compared with nondrinkers was 1.41 (95% confidence interval [CI], 1.16–1.72). Case-control studies suggest a modest-to-strong positive relationship between alcohol consumption and large bowel cancers.[14,15] A meta-analysis found that the association did not vary by sex or location within the large bowel.
Five studies have reported a positive association between alcohol intake and colorectal adenomas. A case-control study of diet, genetic factors, and the adenoma-carcinoma sequence was conducted in Burgundy. It separated adenomas smaller than 10.0 mm in diameter from larger adenomas. A positive association between current alcohol intake and adenomas was found to be limited to the larger adenomas, suggesting that alcohol intake could act at the promotional phase of the adenoma-carcinoma sequence.