Study Examines Colorectal Cancer Screening Effectiveness in Women

Overview of Colorectal Cancer

A recent study investigated whether colorectal cancer screening is as effective in reducing cancer incidence and mortality in women as it is in men. Colorectal cancer ranks as a leading cause of cancer-related deaths globally, being the second leading cause in the United States and the most common cancer in Europe. Screening plays a crucial role in early cancer detection and in lowering both incidence and mortality rates. The primary screening methods include fecal occult blood testing, flexible sigmoidoscopy, and colonoscopy.

Current Colorectal Cancer Screening Guidelines

The existing guidelines recommend that adults undergo fecal occult blood testing, sigmoidoscopy, or colonoscopy every 10 years, starting at age 50 and continuing until age 75. For high-risk populations, screening should commence at age 40. While colonoscopy is a comprehensive option, it is associated with higher costs, specialized expertise, and certain risks, making sigmoidoscopy and fecal occult blood tests more commonly utilized.

These guidelines do not differentiate based on sex. Although men and women are statistically at similar lifetime risk for colorectal cancer, research indicates that women tend to develop the disease almost ten years later than men.

Effectiveness of Screening in Men vs. Women

A recent review published in the BMJ assessed the effectiveness of colorectal cancer screening in women, based on a study of 98,678 adults aged 50 to 64 without a prior history of colorectal cancer. Out of these participants, 20,552 were screened using flexible sigmoidoscopy, while the remaining 78,126 did not undergo screening. Some participants were screened solely by sigmoidoscopy, while others received a combination of sigmoidoscopy and fecal occult blood testing. The study had a mean follow-up of 14.8 years.

The findings revealed a 34% reduction in colorectal cancer incidence and a 37% decrease in mortality among the screened group compared to the control group. However, adding fecal occult blood testing to sigmoidoscopy did not enhance the screening’s effectiveness. In men, the study showed a 0.78% absolute risk reduction in incidence and a 0.33% reduction in mortality. Conversely, the impact of screening on women’s incidence and mortality rates was minimal.

Limitations of Sigmoidoscopy for Women

While the adherence rates for screening were comparable between genders, the study did not find significant benefits of colorectal screening for women. Previous randomized trials indicated that sigmoidoscopy could reduce colorectal cancer incidence by 18-26% and mortality by 22-31%. However, these results were not replicated in women.

Some researchers propose that the delayed onset of colorectal cancer in women, occurring nearly a decade later than in men, may account for the lower effectiveness of screening among females. Current guidelines might initiate screening too early for women, missing cancers that could develop later in life.

Implications for Screening Guidelines

The study’s findings suggest that sex may be a critical factor in colorectal cancer detection. Different detection rates have been observed between men and women, indicating potential benefits from adjusting screening guidelines to consider sex alongside age and family history.

The researchers also concluded that sigmoidoscopy could be effective for a follow-up period of 15 years. Current U.S. guidelines recommend repeating sigmoidoscopy every 5 to 10 years, and extending the intervals may lead to significant cost savings for health departments.

Future Recommendations for Women

In conclusion, the study raises questions about the effectiveness of sigmoidoscopy for colorectal cancer screening in women, showing limited benefits in reducing incidence and mortality. The researchers advocate for these findings to inform the development of future colorectal cancer screening recommendations that ensure equal effectiveness for women and men.

Written by Preeti Paul, MS Biochemistry
Reference: Jacqui Wise. Women see no benefit from colorectal cancer screening, study finds. BMJ 2018;361;k1747 doi: 10.1136/bmj.k1747