Lowering the starting age for colorectal cancer screening from 50 to 45 is a cost-effective strategy to reduce cancer deaths, but improving uptake among those currently eligible would provide even greater benefits, according to U.S. researchers who used a math model to project the outcomes in a study published March 28 in Gastroenterology.
The team, led by Dr. Uri Ladabaum from Stanford University School of Medicine, developed an analytical Markov model to project the effect that lowering the starting age would have on colorectal cancer outcomes in the U.S.
The model matched the clinical predictions of the microsimulation model that the American Cancer Society (ACS) used to guide its decision to lower the screening age for colorectal cancer from 50 to 45 in its latest guideline from 2018. Various groups have intensely debated the extent to which colorectal screening might benefit younger patients and contribute to healthcare costs.
"Our aim was to do a traditional cost-effectiveness analysis, but then also look at the potential trade-offs and national impact," Ladabaum said in a statement from the university. "We wanted to crystallize the qualitative issues into tangible numbers, so people could then have a productive debate about these very issues."
For the study, Ladabaum and colleagues modeled five colorectal cancer screening strategies that relied on different variations of colonoscopy, fecal immunochemical testing, and/or sigmoidoscopy exams. The model projected that lowering the screening age from 50 to 45 for any of the five approaches would reduce the incidence of colorectal cancer and cancer-related deaths at costs ranging from $2,500 to $55,900 per quality-adjusted life year (QALY) gained. (An intervention is generally considered cost-effective if its costs amount to less than $100,000 per QALY gained.)
When only using colonoscopy, the model estimated that starting screening at 45 years would avert four cancer cases and two cancer deaths per 1,000 individuals at a cost of $33,900 per QALY gained. Over the course of five years, screening at a younger age would reduce the number of colorectal cancer cases in the U.S. by 29,400 and the number of colorectal cancer deaths by 11,100.
Though lowering the screening age would increase societal cost by $10.4 billion, the collective benefits would result in an absolute (i.e., cost-effective) gain of 14 QALYs per 1,000 individuals.
| Effect of colorectal cancer screening starting at age 45 vs. 50 | ||
| Starting colonoscopy screening at 50 years | Starting colonoscopy screening at 45 years | |
| No. of colorectal cancer cases | 696,700 | 667,300 |
| No. of colorectal cancer deaths | 244,600 | 233,500 |
| Total costs | $114.7 billion | $125.1 billion |
| No. of colonoscopies | 70.3 million | 80.9 million |
The researchers also used the model to project the effect of allocating the same resources required to start screening individuals at an earlier age to instead bolstering screening uptake in individuals older than 50. The model determined that clinicians would be able to screen an additional 231 previously unscreened 55-year-olds per 1,000 persons. This would lead to better outcomes than simply lowering the screening age to 45 -- averting nearly threefold more cancer deaths at one-third the cost.
However, in yet another hypothetical scenario, lowering the screening age to 45 and also increasing participation (from its current estimated rate of 62% to 80%) would result in even better outcomes than increasing uptake alone. For this scenario, the model projected 38,500 fewer colorectal cancer deaths over five years, compared with the current rate.
"Is screening starting at 45 cost-effective by traditional standards? The answer is yes," Ladabaum said. "But the bottom line for me is that this is nuanced. The crucial question is: Can we screen younger people and at the same time do a better job of screening older and higher-risk people?"
