Screening endoscopy in women under 50 significantly reduces the risk of a colorectal cancer diagnosis at age 55 according to a US study
The use of screening endoscopy in women before the age of 50 is associated with a 55% lower risk of being diagnosed with colorectal cancer (CRC) at age 55. This was the conclusion of a prospective cohort study of US women.
According to the International Agency for Research on Cancer, in 2020 there were almost 2 million colorectal cancer diagnoses and nearly one million deaths, making it the third most commonly diagnosed cancer type in the world.
Although incidence rates among those of screening age have decreased, data from the US shows that among individuals under 50 years of age, the incidence rate has increased by approximately 2% between 2011 and 2016.
According to the American Cancer Society, screening for CRC is associated with a significant reduction in CRC incidence and CRC-related mortality and have recommended that adults aged 45 years and older with an average risk of CRC should undergo regular screening.
Furthermore, long-term follow studies suggest that screening endoscopy is associated with a reduced colorectal-cancer mortality. Nevertheless, there are limited data on the value of screening endoscopy in younger patients.
For the present study, the US researchers used data in the Nurses’ Health Study II, primarily because participants in this prospective registry were aged 26 to 45 at enrolment and this therefore provided an opportunity to examine any potential associations between the age of screening endoscopy and the development of CRC.
Using 1991 as the baseline because this was the first year when questions about screening endoscopy were included, participants were asked in subsequent questionnaires if they had undergone sigmoidoscopy or colonoscopy in the past two years and the reason for this screening.
The primary endpoint was overall CRC incidence although the researchers included the incidence of younger-onset CRC (diagnosed before age 55) and CRC mortality as secondary outcomes.
Screening endoscopy and development of colorectal cancer
A total of 111,801 women with a median of 36 years at enrolment were included in the analysis and followed for 26 years, during which time 519 incident cases of CRC were documented. Compared to women who underwent screening endoscopy age 50 or later, those who underwent a screen before 45 years of age were more likely to have a family history of CRC.
When compared to women who did not undergo screening endoscopy, the adjusted hazard ratios (HRs) for any CRC were 0.37 (95% CI 0.26 – 0.53) for women aged under 45 years, 0.43 (95% CI 0.29 – 0.62) for those 45 to 49 years of age and 0.46 (95% CI 0.30 – 0.69) for those 55 years and older. Hence there was a significantly lower risk of incident CRC when screening was started before the age of 45.
The authors calculated that the absolute reduction in the estimated cumulative incidence of CRC up to age 60 was 72 per 100,00 people if screening endoscopy was started between the ages of 45 to 49 compared to being performed between the ages of 50 to 54.
The risk of being diagnosed with CRC at age 55 was 55% lower if screening was started before the age of 45 (HR = 0.45, 95% CI 0.29 – 0.70) and equally lower (HR = 0.43) when started between the ages of 45 and 49.
The authors concluded that earlier screening endoscopy (before 50 years of age) was associated with a significantly lower risk of both CRC and a diagnosis before age 55.
Ma W et al. Age at Initiation of Lower Gastrointestinal Endoscopy and Colorectal Cancer Risk Among US Women JAMA Oncol 2022