Clinical question
Should we lower the age at which average-risk patients commence colorectal cancer (CRC) screening from 50 to 45?
Bottom line
In developed countries, the incidence of CRC in persons younger than 50 years has increased by 20% to 30% in the past 20 years. However, the absolute risk increase is only 1 to 4 per 100 000 persons. Screening average-risk patients younger than 50 should not be encouraged at this time.
Evidence
There are population-based data on CRC incidence among those younger than 50 in developed countries, but no RCTs examining commencing screening at 45 years versus 50 years are available.
- In Canada, a study1 of those younger than 50 years, comparing 2015 with 1971, found an increased incidence of 1 to 2 per 100 000 (from 10 or 11 to about 12 per 100 000). The relative risk increase (RRI) was about 20%.
- In a study in Alberta2 among those 35 to 49 years old, comparing 2014 with 1995, incidence increased by 4 per 100 000 (from 13 to 17): RRI was about 30%.
— In those younger than 50 years, comparing 2017 with 2010,3 incidence increased by 1 per 100 000 (from 6 to 7): RRI was about 20%.
— Alberta number differences are due to different ages and time frames studied.
- In a US study,4 among those 40 to 49, comparing 2013 with 1992, incidence increased by 4 per 100 000 (from 18 to 22): RRI was about 25%.
Many developed countries report small annual increases in CRC rates in patients younger than 50 years.5
Context
Screening for CRC (between 50 and 75 years old) decreases CRC mortality but not overall mortality.6
Improving screening compliance between those 50 to 75 years old to 80% (currently 55% in Canada7) would prevent about 3 times as many CRCs at a third of the cost of early-age screening.8
The median age of CRC diagnosis has decreased from 72 years (2002) to 66 years (2016).9
In the United States, rectal cancer is the most common CRC subtype in those younger than 50.9
Generally, guidelines recommend screening for CRC in those aged 50 to 75.10,11
Options for screening with RCT evidence6: fecal occult blood testing or fecal immunochemical testing every 1 to 2 years, or sigmoidoscopy every 10 years.11
Implementation
Those older than 75 are unlikely to benefit from screening.6 For those 50 to 75, the decision should be personalized. Patients with substantial comorbidity or functional limitation are unlikely to benefit, as some programs (especially outside primary care)12 offer screening without considering comorbidity.13 Tools (eg, https://eprognosis.ucsf.edu) to help determine the effect of comorbidities and function on life expectancy14 can aid discussions. Fecal immune testing should only be used for asymptomatic patients,15 as it might delay definitive investigations in symptomatic patients.
Notes
Tools for Practice articles in Canadian Family Physician are adapted from articles published on the Alberta College of Family Physicians (ACFP) website, summarizing medical evidence with a focus on topical issues and practice-modifying information. The ACFP summaries and the series in Canadian Family Physician are coordinated by Dr G. Michael Allan, and the summaries are co-authored by at least 1 practising family physician and are peer reviewed. Feedback is welcome and can be sent to toolsforpractice{at}cfpc.ca. Archived articles are available on the ACFP website: www.acfp.ca.
Footnotes
Competing interests
None declared
The opinions expressed in Tools for Practice articles are those of the authors and do not necessarily mirror the perspective and policy of the Alberta College of Family Physicians.
- Copyright© the College of Family Physicians of Canada
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