BACKGROUND AND PURPOSE:

• The USPSTF recommends screening for colorectal cancer using fecal occult blood testing, sigmoidoscopy, or colonoscopy in adults (50 to 75 years of age)
  • Based on data between 10-17 years follow-up
  • Effectiveness in women remains uncertain
• Holme et al. (Annals of Internal Medicine, 2018) examined the long-term effects of flexible sigmoidoscopy screening on colorectal cancer (CRC) incidence and mortality

METHODS:

• Randomized controlled trial (RCT)
  • Adults aged 55 to 64 years without prior CRC
  • Between 1999 – 2000
• Patients were randomized to receive either
  • Screening with flexible sigmoidoscopy with and without additional ‘once only’ fecal blood testing
  • No screening
• Primary outcome
  • Age-adjusted CRC incidence and mortality
• Secondary outcomes
  • CRC incidence and mortality in women and men | In the distal colon (rectum and sigmoid colon) | Proximal colon

RESULTS:

• 98,678 people were included in the study
  • 20,552 in screening group | 78,126 in no screening group
  • Adherence rates: 64.7% in women and 61.4% in men
  • Median follow-up was 14.8 years
• absolute risks for CRC in women – no significant difference
  • 1.86% in the screening group
  • 2.05% in the control group
  • Risk difference: −0.19% (95% CI, −0.49 to 0.11%)
  • Hazard Ratio (HR) 0.92 (95% CI, 0.79 to 1.07)
• Absolute risks for death from CRC in women – no significant difference
  • 0.60% in the screening group
  • 0.59% in the control group
  • Risk difference, 0.01% (95% CI, −0.16 to 0.18%)
  • HR 1.01 (95% CI, 0.77 to 1.33)
• Absolute risks for CRC in men – significant difference (P= 0.004)
  • 1.72% in the screening group
  • 2.50% in the control group
  • Risk difference, −0.78 percentage point (95% CI, −1.08 to −0.48%)
  • HR 0.66 (95% CI, 0.57 to 0.78)
• Absolute risks for death from CRC in men – significant difference (P= 0.014)
  • 0.49% in the screening group
  • 0.81% in the control group
  • Risk difference, −0.33% (95% CI, −0.49 to −0.16%)
  • HR 0.63 (95% CI, 0.47 to 0.83)
• In the screening group, no difference was seen between the ‘once only’ fetal occult blood testing group and the group without occult blood testing

CONCLUSION:

• Sigmoidoscopy screening reduced CRC incidence by 34% and reduced related mortality by 37% in men, minimal to no clinical impact in women
• Reason for minimal difference in women is unclear
• Authors state that

Colonoscopy may be a better screening method than sigmoidoscopy in women, as suggested by others. However, this is uncertain because randomized trials on the effectiveness of colonoscopy screening are still ongoing

Learn More – Primary Sources:

Long-Term Effectiveness of Sigmoidoscopy Screening on Colorectal Cancer Incidence and Mortality in Women and Men: A Randomized Trial

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