Blood or Camera?

Blood tests for colorectal cancer are starting to emerge, with several commercially available and more in development. Because uptake rates for current screening methods are low, these minimally invasive tests hold promise for increasing diagnostic rates? But – are they reliable?

Colonoscopy is a very effective screening device that not only allows gastroenterologists to confirm the presence of cancerous growths in real time, but also facilitates preventative action via the removal of pre-cancerous polyps. The problem is – patients don’t like them, so often fail to attend appointments to spare themselves the discomfort of the preparation and procedure. 

This distaste was illustrated in a study in the United States in which eligible patients were given a choice of screening methods: zero percent selected colonoscopy, 6.5 percent selected fecal immunochemical testing, and 93.5 percent blood-based testing. 

In reality, of course, most patients are not offered such a choice. Alarmingly, a study in northern Europe found that only 42 percent of patients offered a colonoscopy went through with the procedure. 

It’s apparent that patients are slipping through the early diagnosis net. Offering cell-free DNA blood tests for first-line screening might increase uptake rates. However, this report suggests blood tests are not yet advanced enough to be considered a viable alternative. The study concludes that more diagnoses would be missed with blood tests, compared with other screening methods, resulting in more deaths from colorectal cancer.

What do you think? Should we screen more people with inferior sensitivity, or fewer people with greater reliability?