Abstract and Introduction
Abstract
Background: Women and men with colorectal adenomas are at increased risk of colorectal cancer and colonoscopic surveillance is recommended. However, the long-term cancer risk remains unknown.
Aims: To investigate colorectal cancer incidence and mortality after adenoma removal in women and men
Methods: We identified all individuals who had adenomas removed in Norway from 1993 to 2007, with follow-up through 2018. We calculated standardized incidence ratios (SIR) and incidence-based mortality ratios (SMR) with 95% confidence intervals (CI) for colorectal cancer in women and men using the female and male population for comparison. We defined high-risk adenomas as ≥2 adenomas, villous component, or high-grade dysplasia.
Results: The cohort comprised 40 293 individuals. During median follow-up of 13.0 years, 1079 women (5.5%) and 866 men (4.2%) developed colorectal cancer; 328 women (1.7%) and 275 men (1.3%) died of colorectal cancer. Colorectal cancer incidence was more increased in women (SIR 1.64, 95% CI 1.54–1.74) than in men (SIR 1.12, 95% CI 1.05–1.19). Colorectal cancer mortality was increased in women (SMR 1.13, 95% CI 1.02–1.26) and reduced in men (SMR 0.79, 95% CI 0.71–0.89). Women with high-risk adenomas had an increased risk of colorectal cancer death (SMR 1.37, 95% CI 1.19–1.57); women with low-risk adenomas (SMR 0.90, 95% CI 0.76–1.07) and men with high-risk adenomas had a similar risk (SMR 0.89, 95% CI 0.76–1.04), while men with low-risk adenomas had reduced risk (SMR 0.70, 95% CI 0.59–0.84).
Conclusions: After adenoma removal, women had an increased risk of colorectal cancer death, while men had reduced risk, compared to the general female and male populations. Sex-specific surveillance recommendations after adenoma removal should be considered.
Introduction
Colorectal cancer is the third most common malignancy worldwide, and the second most common cause of cancer-related deaths.[1] Screening programs with faecal occult blood tests (FOBT), sigmoidoscopy or colonoscopy have been introduced in many countries.[2] The aim of screening is to reduce cancer incidence through the removal of adenomas, and reduce cancer mortality through incidence reduction and early detection of cancer.[3]
Individuals who have had adenomas removed are considered at increased risk of developing new adenomas and colorectal cancer in the future and are therefore recommended endoscopic surveillance. As adenomas are found in more than 20% of women and 30% of men during screening,[4,5] and screening activity is increasing, the number of individuals recommended for surveillance after adenoma removal is growing rapidly and might limit the availability of colonoscopy resources for diagnostic and therapeutic purposes.[6]
We have previously shown that individuals who have had low-risk adenomas removed have a lower risk of colorectal cancer mortality than the general population,[7,8] a finding later confirmed by others.[9–12] Although individuals who have had high-risk adenomas removed have a higher risk of colorectal cancer death in most studies,[7,8,11,12] the magnitude and duration of excess risk is uncertain due to low precision and usually less than 10 years of follow-up.[11–15] Nevertheless, individuals are currently recommended frequent surveillance colonoscopy after adenoma removal, typically every 3, 5, or 10 years depending on adenoma characteristics.[16–18] These recommendations are based on scarce evidence.
There is emerging evidence that endoscopic screening may convey less benefit in women than in men.[19–21] Thus, it is imminent to investigate if women and men have different risks for colorectal cancer incidence and mortality after adenoma removal, and consider sex-specific surveillance.
We here update our previous report on colorectal cancer incidence and mortality after removal of low- and high-risk adenomas in a large population-based cohort,[7] now with 13.0 years of follow-up and sex-stratified analysis.