Attending at least one surveillance visit with colonoscopy benefited most patients diagnosed with intermediate-risk adenomas, according to the results of a retrospective study published in Lancet Oncology. However, researchers led by Wendy Atkin, PhD, of the Cancer Screening and Prevention Research Group at the Imperial College London, noted that the value of surveillance is unclear in some patients who are already at low risk after baseline colonoscopy.
The study included 253,798 patients who underwent a baseline colonoscopy and polypectomy at one of 17 UK hospitals. Of those, 11,944 patients were diagnosed with intermediate-risk adenomas between 1990 and 2010 and were included in this analysis. Patients were offered surveillance colonoscopy at intervals of 3 years. More than one-half (58%) of patients attended at least one surveillance visit, while 42% of patients attended none.
With a median follow-up of 7.9 years, 210 colorectal cancers were diagnosed.
Patients who attended at least one surveillance visit had a significantly reduced colorectal cancer incidence rate (adjusted hazard ratio [HR], 0.57; 95% CI, 0.40–0.80 for one visit; HR, 0.51; 95% CI, 0.31–0.84 for two visits) compared with patients who had no surveillance.
The researchers divided patients into lower-risk (26%) and higher-risk (74%) subgroups based on polyp and procedural characteristics that have been identified as colorectal cancer risk factors. Without surveillance, patients in the high-risk group had an incidence of 3.3% at 10 years compared with 1.1% for patients in the low-risk group. After a single surveillance visit, the incidence of colorectal cancer at 10 years was 2.8% in the high-risk group and 0.7% in the low-risk group.
Patients with suboptimal colonoscopy, proximal polyps, or a high-grade or large adenoma at baseline who underwent no surveillance had a significantly greater colorectal cancer incidence compared with the general population (standardized incidence ratio [SIR], 1.30; 95% CI, 1.06–1.57). In contrast, patients without these risk factors had a lower colorectal cancer incidence than the general population (SIR, 0.51; 95% CI, 0.29–0.84).
“We conclude from our results that patients diagnosed with intermediate-risk adenomas are at only a small increased risk of developing colorectal cancer after their baseline colonoscopy and polypectomy compared with the general population, especially if they have had a good quality baseline colonoscopy; therefore, it is unclear whether all of these intermediate-risk patients need the currently recommended 3-yearly surveillance by colonoscopy,” the researchers wrote. “Our results emphasize the importance of achieving a complete colonoscopy with good quality bowel preparation. Having a suboptimal quality baseline examination was associated with a doubling in colorectal cancer incidence irrespective of polyp characteristics.”