New research supports qFIT bowel cancer screening from your 40s

The majority of bowel cancer cases are diagnosed in people over 50 years old. But rates of early onset bowel cancer in the under 50s have been rising rapidly and bowel cancer is now the leading cause of cancer death in men aged 20 to 49 and the second leading cause of death in women of the same age¹.

In response to the rising rates of bowel cancer in the under 50s, in 2021 the USA lowered the age for bowel cancer screening to 45. Unfortunately, in the UK, we’ve only just lowered the screening age to 50 and there are no plans to lower it further.

New data from a study in Taiwan suggests this failure to adapt to the changing epidemiology of bowel cancer is costing lives².

What did the researchers do?

In the study by Chiu et al., published last month in JAMA Oncology, researchers offered people across two cities in Taiwan the opportunity to begin bowel cancer screening with a qFIT bowel cancer screening test (which picks up blood in the stool) from age 40. Around 40,000 people took up the offer and were compared to 224,000 people who declined. Both groups continued with Taiwan’s regular bowel cancer screening programme from aged 50.

The researchers followed the two groups up for about 17 years on average and looked at how many people were diagnosed or died of bowel cancer.

What did the study find?

The study found that the group that started qFIT bowel cancer screening in their 40s, had a lower rate of being diagnosed with bowel cancer (incidence) - 26.1 (95% confidence interval, 22.3-29.9) vs 42.6 (95% CI, 40.5-44.7) per 100 000 person-years.

Researchers also found that the rate of dying from bowel cancer (mortality) was lower in the early screening group - 3.2 (95% CI, 1.9-4.6) vs 7.4 (95% CI, 6.5-8.2) per 100 000 person-years.

The benefits of early screening were found in both men and women.

The researchers also conducted a more in-depth analysis where they accounted for factors that might have differed between the two groups such as family history of bowel cancer and the number of screening tests done. This analysis confirmed the crude incidence and mortality rates reported above. Early screening was associated with a 21% (95% CI 6 - 33%) reduction in the risk of being diagnosed with bowel cancer and a 39% (95% CI 2 - 62%) risk reduction of dying from bowel cancer.

Why might early bowel cancer screening be associated with a lower rate of developing bowel cancer?

One particularly interesting finding of this study was that starting bowel cancer screening earlier actually reduced the chance of being diagnosed with bowel cancer. This isn’t necessarily what you might expect as screening could potentially increase the number of cancers found (as you're likely to find asymptomatic cancers that would otherwise have been undetected).

There are two potential explanations for this. Firstly, a qFIT test just looks for blood in the stool. Both bowel polyps and bowel cancers can cause this. It’s possible that qFIT testing picked up people with polyps who then had them removed at colonoscopy. This could prevent bowel cancer developing in the first place, hence the reduction in bowel cancer incidence in the early screening group.

However, an alternative explanation is that the early screening group was healthier than the later screening group to begin with. Remember, this wasn’t a randomised study and people were free to decline or accept early screening as they saw fit. This could have led to fundamental differences between the individuals in the two groups. For example, perhaps individuals who accepted early screening were more likely to engage in other health-related behaviours like exercise and a balanced diet which meant they were less likely to develop bowel cancer to begin with.

Were there any other limitations of the study?

Even though this study involved hundreds of thousands of individuals, the numbers of bowel cancers picked up and the number of bowel cancer deaths in the early screening group was relatively small - 178 bowel cancers diagnosed with 22 deaths. This means that only a few more or less cancer deaths can have quite a large impact on the results. Indeed, this is why the 95% confidence intervals for the in-depth analysis discussed above were quite large and only just reached statistical significance.

What can we take from this study?

We actually don’t have much data to indicate whether beginning bowel cancer screening before the age of 50 is beneficial. Most studies only look at the 50 - 75 year age group and try to extrapolate outcomes to younger age groups.

This study directly demonstrates that starting bowel cancer screening with a qFIT test from your 40s is associated with lower risks of both getting and dying from bowel cancer.

Unfortunately, it’s unlikely that the UK bowel cancer screening programme will lower the start age any time soon. I’ve already commented elsewhere on the inadequacies of bowel cancer screening in the UK and the reality is that we simply don’t have the resources required to deliver screening to individuals in their 40s. Furthermore, even if we had the resources, it's unlikely that the intervention would be considered cost-effective on a population level.

But Selph is all about prioritising you, the individual. If you want the gold-standard when it comes to qFIT bowel cancer screening - starting in your 40s, testing yearly and with an appropriate threshold for proceeding to colonoscopy - you’re going to have to arrange this yourself.

In fact, we're so passionate about making qFIT bowel cancer screening available to the under 50s, that we've partnered with bowel cancer charity 40tude, to deliver free qFIT bowel cancer screening to individuals who wouldn't be eligible under the national screening programme.