The incidence of colorectal cancer (CRC) was found to be reduced by 67% with polypectomy and by 70% with adenomatous or advanced histology polypectomy in patients undergoing 24 years of follow-up in the Minnesota Colon Cancer Control Study (MCCCS), according to research published in Gastroenterology.
Investigators reported extended results from the MCCCS after 24 years of follow-up; previous study results were based on 18 years of follow-up. The objectives of the current analysis were to examine the effect of polypectomy on CRC incidence and to study the differences in outcomes after polypectomy by sex and age older and younger than 65 years.
Participants underwent fecal occult blood test screening consisting of 6 guaiac-impregnated paper slides. Diagnostic colonoscopy was offered to participants who had at least 1 positive slide. Polyps were removed during the procedure and sent for analysis.
A total of 46,445 participants (average age, 62.2 years; 51.9% women) were randomly assigned to 1 of 3 arms: annual CRC screening (annual), biennial CRC screening (biennial), or usual care (control). Among the 31,082 participants in the screening arms, 11,518 (37%) underwent at least 1 colonoscopic examination during the follow-up period. Of this group, 3542 (31%) had at least 1 polyp detected, and 3109 (27%) underwent removal of at least 1 polyp. Of the 3109 participants in the screening arms who underwent polypectomy, 1408 (45%) had more than 1 polyp removed.
A total of 5806 polyps were removed in the screening arms, and the average polyp size was 7.5 mm. Approximately half of the polyps were adenomatous (48%), and the most common location for polyps was distal (63%). Colorectal cancer was diagnosed in 926 (3.0%) and 560 (3.7%) patients in the screening and control arms, respectively, in the 24 years of follow-up and 862,669 person-years of follow-up.
According to the investigators, the instrumental variable (IV)-adjusted estimated relative cumulative CRC incidence rate due to any polypectomy was 0.33 (95% CI, 0.23-0.48); when polypectomy was limited to only adenomatous or advanced histology polyps, the CRC incidence rate was 0.30 (95% CI, 0.20-0.44). When the intervention was polyp detection rather than polypectomy, the IV-adjusted estimated relative cumulative CRC incidence rate was 0.35 (95% CI, 0.25-0.50) for all polyps detected and 0.31 (95% CI, 0.21-0.45) for adenomatous or advanced histology polyps.
The IV-adjusted relative cumulative CRC incidence rate for any polypectomy differed depending on sex (relative risk [RR] 0.41, 95% CI, 0.25-0.66 for men and RR 0.24, 95% CI, 0.14-0.40 for women), but this difference was not found to be statistically significant (P =.11). The IV-adjusted relative cumulative CRC incidence rate after polypectomy was found to be similar based on age (RR 0.31, 95% CI, 0.21-0.48 for participants aged <65 y and RR 0.31, 95% CI, 0.17-0.58 for those aged ≥65 y).
“These findings strengthen our knowledge about long-term benefits of polypectomy and provide information for patient–physician shared decision making when weighing risks and benefits of colonoscopy and polypectomy,” the researchers concluded. “Our study supports the current practice of searching for and removing polyps at colonoscopy.”
Shaukat A, Shyne M, Mandel JS, Snover D, Church TR. Colonoscopy with polypectomy reduces long-term incidence of colorectal cancer in both men and women: extended results from the Minnesota Colon Cancer Control Study. Gastroenterology. Published online November 17, 2020. doi:https://doi.org/10.1053/ j.gastro.2020.11.014