A systematic review of the time of progression of colorectal polyps to symptomatic malignancy

Aims The primary aim of this systematic review was to synthesize evidence on the timeline of colorectal polyp progression to malignancy. Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality globally, and majority of them are known to start as benign polyps which progress to malignancy over time. This means colonoscopy with polypectomy can prevent cancers. However, polypectomy comes with risks of complications which can be life limiting, especially in patients with co-morbidities, whose life expectancy might be less than the time of polyp progression to cancer. Understanding polyp dwell time would be helpful for supporting decision-making about risks and benefits of polypectomy in such patients.

Methods EMBASE, MEDLINE, Scopus and CINAHL databases were searched from January 1960 to July 2023 using Boolean operators with search terms: colonic polyps or adenoma or adenomatous polyps or serrated polyps or adenocarcinoma AND disease progression or progression or natural history or timeline or sojourn time or growth time. Studies that reported the progression of polyps over a period of time in patients followed up by radiological or endoscopic assessment were included. Modelling studies that estimated dwell time were also included. Studies reporting polyps with accelerating factors such as inflammatory bowel diseases or genetic syndromes were excluded [1] [2] [3] [4] [5]. Quality of studies was assessed using Newcastle Ottawa Scale for observational studies and a risk of bias tool for assessment of modelling studies. Heterogeneity of study characteristics precluded meta-analysis therefore a narrative synthesis was produced following SWiM guidance.

Results 7 observational studies and 4 modelling studies met the inclusion criteria. Observational studies had small number of patients (range 17-305) and included few CRCs (range 2-21). One study did not report number of patients, but reported 408 adenomas. There was a large variation in reported dwell time in currently available studies. In observational studies, mean dwell time ranged from 1.8 years (in a Japanese study of 17 patients followed for a mean of 1.7 years in whom 8 CRCs were diagnosed) to 9.25 years (in a Japanese study of 408 adenomas, followed for a mean of 3.6 years, in whom 3 CRCs were diagnosed). In modelling studies time from advanced polyp to malignancy and from polyp incidence to in-situ malignancy was estimated to be between 3.6 to 41.6 years.

Conclusions The evidence for polyp dwell time is scanty. Randomised controlled trial would have significant ethical barriers, but a large observational study would be useful to shed further light on polyp dwell time and help inform management decisions and clinical guidelines, especially in patients whose life expectancy is less than the expected dwell time.

Publication History

Article published online:
27 March 2025

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