Don’t let perfect be the enemy of the good in colon cancer screening
Volume 11, Issue 19 | May 8, 2025
ALSO IN THIS ISSUE
mRNA in liquid biopsy could improve cancer Dx
Conclusions on post-cancer surveillance outdated
USDA axes new testing for salmonella rule
Measles Outbreaks: Death count now three
USDA axes improved consumer protection from salmonella
On April 25, the USDA nixed a new rule that would have given the agency the ability to better prevent salmonella-contaminated poultry from reaching consumers. Before the rule was proposed, the agency was only able to test food for the microbe once it was already being sold to the public.
COMMENTARY: We’re kind of amazed that the USDA didn’t already have the authority described in the new rule - to test food during the manufacturing process. To see this important improvement in public health being rolled back is somewhere between disappointing and scary.
Focus on mRNA in liquid biopsy could improve cancer Dx
Last month, Nature published a paper that describes an ultrasensitive method for detecting and analyzing cell-free messenger RNA (mRNA) in the bloodstream. The researchers showed that the technique could be used not only to diagnose cancers and to learn why a cancer might be resisting treatment, but also to see evidence of microscopic injury to organs for reasons other than cancer, like infectious disease, autoimmune disorders, or even smoking.
COMMENTARY: Why is this important? First, a little background. Cancer diagnostics began by focusing on DNA mutations. But the actual damage happens when that mutant DNA gets transcribed into proteins by mRNA. Detecting the location and abundance of these rogue proteins would be ideal, but we can’t do that with liquid biopsy yet.
A lot of recent advances in liquid biopsy have focused on cell-free DNA (cfDNA) in the bloodstream. However, cell-free mRNA (cfRNA) offers many improvements over cfDNA:
Not all DNA mutations get transcribed into mRNA.
cfRNA can help identify what cells and tissues are involved in a cancer and what its level of progression is.
DNA mutations are only one of many sources of changes in mRNA.
DNA fragments are only released into the bloodstream when a cell dies, but some mRNA fragments are released before then.
One big argument against using blood-borne cfRNA is that about 95% of it isn’t mRNA - it's the ribosomal RNA that makes up the cellular structures that manufacture proteins. But the researchers used a combination of physical and algorithmic techniques to solve that problem.
As liquid biopsy for cancer diagnosis continues to develop, we see at least two divergent directions for the field. One is pan-cancer early detection, which continues to face the knotty problem of its low positive predictive value. The other is diagnosis after treatment, for which the technique described in this paper is a significant step. Both will clearly be needed.
Measles Outbreaks: Death count now at three
Measles cases in North America 11x higher than last year
TX outbreak may be slowing
ND outbreak affects schools
The US measles death count this year now stands at three, with the confirmation that an adult in New Mexico died of measles earlier this year.
A Pan American Health Organization report noted that measles cases in North America are 11x higher than last year, with most of the cases in Canada (1,177), the US (over 900), and Mexico (428 as of April 16).
According to Your Local Epidemiologist, the outbreak in West Texas may be slowing. This week they noted fewer reported cases, fewer anecdotal reports of new cases from doctors, and - for the first time since the start of the outbreak - no children hospitalized with measles.
In North Dakota, four unvaccinated people with measles were present in local schools while they were infectious. As a result, the schools in that area are requiring unvaccinated people to isolate for 21 days, which is the maximum possible incubation time for the disease.
The current larger outbreaks are shown below. The cases in Texas, New Mexico, Kansas, and Oklahoma all came from the same source; those in Indiana, Michigan, Montana, North Dakota and Ohio are unrelated.
Colon-cancer screening: Don’t let perfect be the enemy of the good
For colon-cancer detection, colonoscopy is the gold standard, with molecular stool testing close behind. But lots of people don’t get screened at all.
In 2006, Kaiser Permanente Northern California started sending a fecal immunochemical test (FIT) to patients when it reminded them that they needed to get screened for colon cancer. Now researchers have studied whether doing so changed colon-cancer screening rates or rates of disease and death. (Spoiler alert: It did. By a lot.)
The study, presented at Digestive Disease Week 2025, included 1.1 million patients ages 50 - 75. It showed that colon-cancer screening across all racial and ethnic groups increased from 37% in 2000, before the program began, to 80% in 2019.
Cancer cases initially went up, likely due to diagnoses in people who were either late getting screened or had never been screened at all. But eventually, new cases went down by 30% compared to levels in 2000, and deaths were cut in half.
The initiative also brought the colon cancer death rate in Black patients - who typically get and die from colon cancer more frequently than folks of other ethnicities - from 52 per 100K down to 24 per 100K. (Deaths in Hispanic, White, and Asian patients fell to about 20 per 100K.)
COMMENTARY: Wow! It is rare to see any program that works so effectively, especially one with more than a million people running more than a decade. This initiative shows that education works.
Kaiser chose to use a simple at-home test to make screening easy and broadly accessible. They recognized that the majority of these people were not going to get a colonoscopy. So, instead of insisting on a “gold standard” that some people just weren’t willing to do, they decided to encourage as many folks as possible to get at least some screening. It saved lives.
COMMENTARY: Conclusions on surveillance after cancer treatment based on outdated evidence
NEJM recently published a potentially misleading “Perspective” (paywall) concluding that the mortality benefits of frequent check-ups for people who have completed their cancer treatment are questionable, and the harms (anxiety and cost) are significant. We have to take serious issue with the conclusions advocated here. At best they apply only to cancer survivors who have had successful curative therapy and only for as long as these patients remain completely asymptomatic.
However, the evidence cited in support of even these more limited conclusions is 15 - 25 years old. Sure, with the diagnostic and treatment options available at that time, evidence of surveillance mortality benefit is mixed. But those days are gone.
In today’s world, a growing number of effective personalized treatment options are available to treat metastasis, and liquid biopsies can detect and characterize malignancies before they are large enough to be detectable with imaging. We need to know more about how well our current surveillance methods work in light of these advances. Perhaps we do need to update our methods. But we can’t be sure until we have more up-to-date data.
Smart watches are great, but sometimes low-tech is all you need. In a study of about 4,200 middle-aged folks, the number of steps a person took per day and how fast they walked captured about 88% of the health information gathered by an accelerometer (the tech inside a smart watch).
If your lower back feels like Liz’s does this week, you may have been wondering whether you need an MRI. You probably don’t, as long as your symptoms don’t include any red flags that suggest serious disease. New research in 100 patients showed that X-rays predicted MRI results in about 75% of the cases involving common lower-back problems.