Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer and the second leading cause of cancer death in Canada. For decades, cancer screening guidelines focused on adults aged 50 and older, who historically carried the greatest risk. That picture is changing.
Since the mid-1990s, rates of colorectal cancer in Canadians under age 50 have been rising steadily. This shift has been observed across many Western countries and is now well documented. The causes are not fully understood, but increasing rates of obesity, ultra-processed food consumption, and possibly early-life exposure to certain gut bacteria are among the suspected drivers.
In response, the United States, Australia, and other countries have already lowered their recommended screening start age from 50 to 45 years. Canada's current national guidance still recommends starting at age 50, and this study was conducted to rigorously evaluate whether Canada should follow suit.
The faecal immunochemical test (FIT) is a simple, non-invasive screening method. A person provides a small stool sample at home and mails it to a lab. The test detects tiny amounts of blood in the stool that may signal the presence of colorectal cancer or pre-cancerous polyps, often before any symptoms appear.
Canada's existing CRC screening programs are organized around FIT testing every 2 years (biennial FIT). Most provinces send test kits to eligible residents and follow up with colonoscopy for anyone who has a positive result. This organized, population-based approach has helped reduce colorectal cancer mortality among Canadians aged 50 to 74.
FIT is considered particularly well-suited for population-scale screening because it is inexpensive, requires no preparation, can be done privately at home, and avoids the invasiveness of colonoscopy. Evidence from large randomized trials confirms that FIT-based screening is comparable in effectiveness to colonoscopy-based screening when offered to a population, while generally achieving higher participation rates.
The research team used two complementary methods. First, they analyzed national cancer registry data from the Canadian Cancer Registry, tracking colorectal cancer incidence and mortality by age group from 1971 through 2022. This allowed them to establish whether CRC rates in younger Canadians were genuinely rising and by how much.
Second, they used the OncoSim-Colorectal model, a well-validated computer microsimulation tool developed for Canadian cancer policy. This model simulates the entire Canadian population over time, projecting what would happen to cancer cases, deaths, and costs under different screening scenarios.
The team compared two scenarios: the current policy of starting FIT screening at age 50 and a proposed change to start at age 45. Both scenarios assumed biennial FIT testing ending at age 74, with 43 percent participation and 80 percent adherence to follow-up screening, based on real Canadian survey data. The simulation ran from 2025 to 2071 to capture lifetime effects across multiple birth cohorts.
Analysis of Canadian Cancer Registry data confirmed that absolute colorectal cancer incidence rates in adults under 50 have increased continuously, with the most dramatic rise beginning after 1996. In 2022, CRC rates in 45- to 49-year-olds ranged from 33.8 per 100,000 in British Columbia to 43.6 per 100,000 in Newfoundland and Labrador, reflecting a notable east-west gradient across Canada.
Relative incidence analysis by birth cohort revealed an even more concerning pattern. Compared to Canadians born between 1953 and 1957, every successive generation has faced a significantly higher risk of developing colorectal cancer. The youngest cohorts studied, those born in the early 1990s, face the greatest relative increase of all.
Importantly, these rising trends continued through 2022, even accounting for the disruptions of the COVID-19 pandemic. This consistency strengthens the case that the trend is real and not merely an artifact of health system fluctuations. Canada's incidence rates in adults under 50 now exceed the rates that originally motivated the United States and Australia to lower their screening ages to 45.
The microsimulation model estimated that lowering the FIT screening start age from 50 to 45 would result in 15,070 fewer colorectal cancer diagnoses and 6,100 fewer CRC deaths in Canada between 2025 and 2071. These are substantial numbers representing real lives saved and cancers prevented.
Expressed another way, for every 100 additional follow-up colonoscopies performed after a positive FIT, the model predicts 3.5 fewer CRC cases and 1.4 fewer deaths. For every 1,000 additional FIT tests done, 2.2 fewer cancers and 0.9 fewer deaths would result. These rates of cancer prevention per procedure are meaningful and comparable to what is achieved in older age groups.
The reductions were most prominent in the 50- to 54-year-old age group, because screening at 45 catches pre-cancerous polyps before people enter their 50s. The benefits then ripple upward through all age groups, reflecting the lasting impact of earlier intervention on the natural history of the disease.
A common concern about expanding screening eligibility is cost. Screening more people requires more tests, more follow-up colonoscopies, and more healthcare resources. However, this study found that starting FIT at age 45 would lead to an estimated net cost savings of $233 million CAD over the lifetimes of the eligible cohorts.
This savings occurs because the costs of expanded screening are more than offset by reductions in cancer diagnosis and treatment costs. Treating colorectal cancer, particularly at advanced stages, is expensive and becoming more so as targeted therapies and immunotherapy become standard of care. Every cancer prevented saves substantial downstream treatment costs.
If anything, the model likely underestimates the savings. It does not account for indirect costs such as lost productivity or out-of-pocket expenses for patients and caregivers, which represent about 25 percent of direct healthcare costs. Nor does it fully capture the rapidly rising cost of modern cancer treatments, which means future cancer care will be even more expensive than modeled, amplifying the cost-benefit of prevention.
The authors recognize that expanding screening eligibility will increase demand for colonoscopy services, which are already under strain. They outline practical strategies to manage this transition without harming existing programs for the 50-to-74 age group, which remains the population with the highest absolute risk.
One approach, modeled on Australia's experience, would be to immediately lower eligibility to age 45 so that 45-to-49-year-olds can request a FIT kit through their doctor, while formal invitation letters continue to go out only from age 50. This allows gradual uptake in the younger group without overwhelming colonoscopy capacity overnight.
A staggered rollout is another option, where the eligible age drops by one year annually, starting at 49, then 48, and so on. The United Kingdom used a similar approach when it lowered its screening age from 55 to 50. Either approach would give health systems time to build capacity while beginning to capture the benefits of earlier detection.
The study also emphasizes that any expansion must be paired with equity considerations, ensuring that newly eligible individuals in underserved communities are actively recruited rather than left behind, as early data from the United States suggests that overall screening among older groups is not displaced when younger groups are added.
This study brings together updated cancer registry data, rigorous population modeling, and international context to make a compelling case that Canada should lower the starting age for organized FIT-based colorectal cancer screening to 45 years.
The scientific evidence is clear: colorectal cancer rates in younger Canadians are rising, screening at 45 would prevent thousands of cases and deaths, and the long-term economics favor action. The remaining questions are largely about implementation, specifically how to expand the program without straining existing colonoscopy capacity or displacing older Canadians from access.
For individuals in their mid-40s, this research is directly relevant. If you are approaching 45 and live in Canada, this study suggests you may benefit from asking your doctor about colorectal cancer screening options. Awareness, participation, and early detection remain the most powerful tools available against this preventable cancer.