27 Jun, 16 | by EBM
By Dr. Geoffrey Modest
The USPSTF just published their 2016 guidelines for colorectal cancer screening (see doi:10.1001/jama.2016.5989).
- Colorectal cancer is the second leading cause of cancer death in the US
- In 2016, estimates are that 134K people will be diagnosed with the disease, and 49K will die from it.
- Most frequent age range for diagnosis is 65-74, median age of death is 68
- About 1/3 of adults never get screened
Recommendations, for asymptomatic adults at average colorectal cancer risk:
- Screen from age 50-77 (grade A recommendation)
- Screen from age 76-85 (grade C recommendation), as an individual decision, taking into account the patient’s overall health and prior screening history. specifically focusing on:
- Adults in this age group who have never been screened (higher likelihood of abnormality)
- Those healthy enough to undergo treatment if cancer is detected and do not have comorbid conditions that would significantly limit their life expectancy
- They conclude “with moderate certainty that the net benefit of screening in adults aged 76-85 who have been previously screened in small”
- The benefit of screening >85yo is likely to be very small, since the time between detection/treatment and the actual mortality benefit can be substantial
- 7 screening options:
- Guaiac fecal occult blood test (gFOBT) every year
- Fecal immunochemical test (FIT) every year
- Multitargeted stool DNA test (FIT-DNA) every 1 or 3 years (this test combines a FIT with testing for altered DNA biomarkers, has higher sensitivity than FIT but more false positives and leads to more colonoscopies, with their attendant risks). The manufacturer recommends every 3 years
- Colonoscopy every 10 years
- CT colonography every 5 years
- Flex sigmoidoscopy every 5 years
- Flex sig every 10 years, plus FIT every year
- They do not prioritize the order, noting that all of these tests have benefit, and that the main goal is screening (with the hope that multiple different options will increase the screening rate)
- The harms of screening increase with age, going from small in those 50-74, to small-to-moderate in those >75, especially for colonoscopy
- They provide a bar graph of benefits and harms, noting
- Life-years gained per 1000 screened: in the 260-270 range for colonoscopy and FIT-DNAevery year; 240-250 for FIT, gFOBT, CT colonoscopy, and flex sig/ FIT; in the 220 range for flex sig and for FIT-DNA every 3 years
- For colorectal cancer deaths averted per 1000 people screened: 23-24 for colonoscopy, flex sig/FIT and FIT-DNA every year; 22 for FIT, gFOBT, CT colonoscopy; 20 for flex sig or FIT-DNA every 3 years.
- For harms per 1000 screened: lowest (9-11) for flex sig/FIT, FIT-DNA every 3 years, FIT, gFOBT, CT colonography, and flex sig/FIT; 12 for FIT-DNA every year and highest (15) for colonoscopy
- For lifetime burden of colonoscopies per 1000 screened: under 1820 for FIT-DNA every 3 years , FIT, CT colonography and flex sig; 2200-2300 for gFOBT and flex sig/FIT; 2662 for FIT-DNA every year; 4069 for colonoscopy.
- I agree with them that the most important thing is doing the screening, since the benefits really are not that different by which test is done, and that offering noninvasive testing is clearly attractive to many patients (and may increase the screening rate). I would certainly add that any person getting a non-colonoscopic screen should understand and agree to pursuing colonoscopy if positive
- Note that the above numbers are from different studies in different populations and are not based on head-to-head comparisons of different screening strategies, so the actual numbers above (risks/benefits) are not really strictly comparable. But they do probably provide a reasonable ballpark estimate
- For the recently released Canadian guidelines, see http://blogs.bmj.com/ebm/2016/03/04/primary-care-corner-with-geoffrey-modest-md-colorectal-screening-guidelines-from-canada/ , which is pretty dismissive of colonoscopy screening, are not in favor of screening those >74 yo, and actually mostly support using gFOBT or FIT every 2 years or flex sig every 10 years. This blog includes my additional concerns about colonoscopy, where the risk does increase significantly with age, and argues that the lesions that benefit from screening are basically the ones the sigmoidoscope reaches.
- I am concerned about using CT colonoscopy (radiation exposure, competence/accuracy in different settings esp if not done regularly, pick up of incidental non-colon findings which lead to unnecessary testing) and the FIT-DNA testing. For the latter, what does one do if the FIT-DNA is positive but the colonoscopy is negative? Is it a false positive, or is there a small cancer lurking in the crypts? Should there be a follow up colonoscopy in 1 year. What if that is negative — keep repeating it every 1-2 years??? Seems to me to be a black hole, and we should avoid that event horizon.
- They do not suggest a different strategy for Black or Alaska Native individuals (who have higher incidence and mortality than the general population) because there are no empirical data on the effectiveness of different screening strategies for these populations. And there are some studies showing that equal treatment seems to produce equal outcomes, suggesting that the issue may be more of access than actual risk.
- So, my own approach is evolving, though I am much more strongly leaning towards FIT testing alone or in combination with flex sig, since these options seem to maximize the benefit and cut in half the number of colonoscopies with their associated intensive prep, conscious sedation, and increased risk of perforation (all worse in older people), and with small apparent benefit.