The title of this piece is that of a paper published by JAMA Internal Medicine. It is available at the end of this article. If you are a long-time reader of this site, you will appreciate that I have long been skeptical about the utility of screening for cancer. This view may seem odd to the general reader; indeed the physician may find it equally perplexing. What could be disputatious about “catching it before it spreads?”
Two problems must be dealt with before accepting the slogan as truth. The first is that cancer starts small and for a while is curable until it exceeds a critical mass at which point it becomes increasingly difficult to treat. This is not an unreasonable assumption, but it’s still conjecture. Secondly, it is equally possible that the fate of some malignancies is determined by or about the appearance of the first malignant cell. In other words, it is the nature of the tumor that determines its lethality rather than the moment it can be detected.
Physicians supposedly trained in the basics of scientific method and evidence-based medicine are masters of leaps of faith. As soon as a new technique appears many abandon science and, out of a sincere desire to help or alas profit from a new test, make recommendations not based on cool scientific analysis.
The paper under this discussion emanates from Oslo, Norway. Its abstract follows:
| IMPORTANCE Cancer screening tests are promoted to save life by increasing longevity, but it is unknown whether people will live longer with commonly used cancer screening tests. DATA SOURCES A systematic review and meta-analysis was conducted of randomized clinical trials with more than 9 years of follow-up reporting all-cause mortality and estimated lifetime gained for 6 commonly used cancer screening tests, comparing screening with no screening. The analysis included the general population. MEDLINE and the Cochrane library databases were searched, and the last search was performed October 12, 2022. STUDY SELECTION Mammography screening for breast cancer; colonoscopy, sigmoidoscopy, or fecal occult blood testing (FOBT) for colorectal cancer; computed tomography screening for lung cancer in smokers and former smokers; or prostate-specific antigen testing for prostate cancer. DATA EXTRACTION AND SYNTHESIS Searches and selection criteria followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guideline. Data were independently extracted by a single observer, and pooled analysis of clinical trials was used for analyses. MAIN OUTCOMES AND MEASURES Life-years gained by screening was calculated as the difference in observed lifetime in the screening vs the no screening groups and computed absolute lifetime gained in days with 95% CIs for each screening test from meta-analyses or single randomized clinical trials. RESULTS In total, 2 111 958 individuals enrolled in randomized clinical trials comparing screening with no screening using 6 different tests were eligible. Median follow-up was 10 years for computed tomography, prostate-specific antigen testing, and colonoscopy; 13 years for mammography; and 15 years for sigmoidoscopy and FOBT. The only screening test with a significant lifetime gain was sigmoidoscopy (110 days; 95% CI, 0-274 days). There was no significant difference following mammography (0 days: 95% CI, −190 to 237 days), prostate cancer screening (37 days; 95% CI, −37 to 73 days), colonoscopy (37 days; 95% CI, −146 to 146 days), FOBT screening every year or every other year (0 days; 95% CI, −70.7 to 70.7 days), and lung cancer screening (107 days; 95% CI, −286 days to 430 days). CONCLUSIONS AND RELEVANCE The findings of this meta-analysis suggest that current evidence does not substantiate the claim that common cancer screening tests save lives by extending lifetime, except possibly for colorectal cancer screening with sigmoidoscopy. |
Now observe the findings in the following table from the paper -click to enlarge it. Pay attention to the last column. It shows the days of life gained or lost with screening. Note that the unit is days. Also, realize that if the data straddle zero they are statistically insignificant.
If this paper presents a true representation of the value of cancer screening, one would have to concede that the last half century of intensive screening for cancer has been a walk in a dark wood. Even if the study is 100% correct I do not think it will have any effect on how we approach the diagnosis of cancer. We are too wedded to screening to give it up. It’s an emotional issue not one of science. Besides, medicine is sweeter when taken with just small doses of science otherwise it can be very bitter. And of course, it’s just one study. We’d need a lot more showing the same results to justify a course change.
