Screening Reduces Colon Cancer Death

In a 30-year follow-up of participants in the Minnesota Colon Cancer Control Study, researchers found that annual screening with fecal occult-blood testing reduced the risk of death from colon cancer by 32%. This sustained reduction in colorectal cancer mortality reflects the effectiveness of polypectomy—removing colorectal polyps from patients [N Engl J Med. 2013;369(12):1106-1114].

Lead investigator Aasma Shaukat, MD, MPh, associate professor at the University of Minnesota School of Medicine, spoke with First Report Managed Care, and agreed that polypectomy is an effective treatment strategy. “Fecal occult-blood testing alone does not reduce colorectal cancer mortality, but it is the follow-up colonoscopy and detection of early cancers and polypectomy that follow a positive fecal occult-blood test that has an impact,” said Dr. Shaukat. “At 30-plus years of follow-up, the reduction in colorectal cancer mortality is likely due to the effect of polypectomy of polyps that may have turned into cancer 20 to 30 years later if left in place.”

Randomized trials of colorectal cancer screening with fecal occult-blood testing have consistency shown reduction in mortality from colon cancer. However, the duration of benefit is unknown, as are the effects specific to age and sex. Using data from the Minnesota Colon Cancer Control Study, which included 46,551 healthy participants aged 50 to 80 years who were randomized to annual screening, biennial screening, or usual care, Dr. Shaukat and colleagues compared usual care with annual and biennial screening for colorectal cancer with fecal occult-blood testing from 1976 to 1982 and from 1986 to 1992. In total, 11 screenings were offered to participants in the annual-screening group and 6 to those in the biennial-screening group. The study’s aim was to assess the long-term effect of screening on colorectal cancer mortality and all-cause mortality and to evaluate the effects specific to age and sex. National Death Index data was used to measure death from baseline through 2008. The primary end point was colorectal cancer mortality.

At 30 years of follow-up, 33,020 participants (70.9%) died. A total of 732 deaths were attributed to colorectal cancer: 200 of the 11,072 deaths in the annual-screening group; 237 of the 11,004 deaths in the biennial-screening group; and 295 of the 10,944 deaths in the control group. The findings also showed that annual and biennial screening with fecal occult-blood testing reduced colorectal cancer mortality (relative risk [RR] with annual screening, 0.68; 95% confidence interval [CI], 0.56-0.82; RR with biennial screening, 0.78; 95% CI, 0.65-0.93). Although fecal occult-blood screening was associated with a reduced RR of colorectal cancer mortality in both screening groups, there was no reduction observed in all-cause mortality (RR with annual screening, 1; 95% CI, 0.99-1.01; RR with biennial screening, 0.99; 95% CI, 0.98-1.01).

In analyses according to age and sex, the findings showed that a reduction in colorectal cancer mortality was larger for men than for women in the biennial-screening group (P=0.04 for interaction). The American Cancer Society recommends that women be screened for colorectal cancer beginning at 50 years of age for early detection. However, the researchers did not observe any benefit from screening among women <60 years of age.

“Ours is the first study to examine age and gender subgroups,” said Dr. Shaukat. “Our finding of women [aged] 50 to 60 [years] not deriving benefit from screening is hypothesis generating and needs to be studied and confirmed in future studies.”

Considering the findings that more men benefit from colon cancer screening compared with women, Dr. Shaukat added, “Men have a higher risk of colon cancer as well as a higher risk of dying from colon cancer compared to women. [Thus] one would expect the benefit of screening to be larger.”

The researchers noted that data from the study were limited by use of records from the National Center for Health Statistics, lack of screening history information after the trial ended, and no information about the cancer site in the colon.