Studies have shown that colorectal cancer (CRC) incidence is equal between men and women. However, several studies have demonstrated lower adenoma detection rates in women than in men. Many questions arise about differences in adenomas, CRC, and screening practices between men and women: should screening be the same for both sexes, are there differences in risk factors in the formation of colon cancer, should special groups of women be screened differently from the general population, are colonoscopies tolerated differently in women and why, and what determines if a woman will undergo colonoscopy? This article reviews these issues.
Colorectal cancer (CRC) has the second highest cancer-related mortality rate in the United States and is the third most common cause of cancer in women. It is believed that there is an adenoma-cancer paradigm, and target interventions for CRC focus on adenoma detection and removal, primarily with optical colonoscopy. In fact, colonoscopy is considered to be the most effective method for screening and diagnosis of CRC. Studies have shown that CRC incidence is equal between men and women. However, several studies have demonstrated lower adenoma detection rates in women than in men. Many questions arise about differences in adenomas, CRC, and screening practices between men and women: should screening be the same for both sexes, are there differences in risk factors in the formation of colon cancer, should special groups of women be screened differently from the general population, are colonoscopies tolerated differently in women and why, and what determines if a woman will undergo colonoscopy? This article reviews these issues.
Colorectal cancer in women
The lifetime risk of developing CRC is 5.12% in men and women. It is estimated that 142,570 men and women (72,090 men and 70,480 women) will be diagnosed with CRC in 2010, accounting for 10% of all new cancer cases in women. This figure translates to a 41.7 per 100,000 incidence rate in women per year. The cancer burden is sizeable; for example, on January 1, 2007, in the United States there were approximately 1,112,493 men and women alive who had a history of cancer of the colon and rectum, more than half of these being women.
The incidence rates of CRC have decreased from 1998 through 2004 in both men and women, likely from the increased use of colonoscopy driving the increase in CRC screening. Despite the decreased incidence rates, it is still the third most common cancer in the United States and the second leading cause of cancer death among men and women. An estimated 50,000 men and women die each year from CRC; 25,000 of these deaths occur in women, accounting for 9% of all cancer deaths in women. Data on cancer cases collected by the Surveillance Epidemiology and End Results (SEER) database and data on United States population collected by the US Census Bureau suggest that the incidence and mortality are slightly lower in women than in men, with a decline in mortality of 1.1% per year over 10 years in both men and women.
Since 1990, there has been a dramatic decline in mortality, by 32% in men and 28% in women. At the same time, there has been an increase in CRC screening among individuals 50 years of age and older. It is estimated that currently 50% of the population in the United States undergo screening. Other factors that may have contributed to a decrease in CRC mortality include hormone replacement therapy given to many women at the onset of menopause during the 1970s and 1980s (which might protect against CRC), and the increased use of aspirin for cardiovascular disease and nonsteroidal anti-inflammatory drugs for musculoskeletal disorders, which reduce the risk of colon polyps and CRC. The role of estrogen in the development of CRC is discussed later in the article.
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