Our intuition tells us that, if we are able to detect cancer early, before symptoms develop, we can save lives. This would point toward the need to increase the use of “screening” tests to unearth hidden cases before they advance enough to produce symptoms. The question of whether cancer screening truly saves lives is becoming increasingly relevant given the growing enthusiasm for multi-cancer detection blood tests ie, liquid biopsies, PSA blood tests, X-ray mammography, and others. We also need to know whether clinical trials of screening for targeted cancers will reduce not only those targeted cancers, but also overall deaths as well. Now new research casts doubt on the value of screening. In order to explore this question a recent study evaluated a series of calculations of selected cancers (breast, colorectal, liver, pancreas, and prostate) as well as total mortality.
In order to determine whether specific cancers are prevented, or life is extended, the study evaluated pooled data from several prior studies (meta-analyses) employing commonly used cancer screening tests. In an evaluation of 18 long-term randomized clinical trials involving 2.1 million individuals, they found that colorectal cancer screening with sigmoidoscopy prolonged life by 110 days, while fecal testing and mammography screening did not prolong life. A probable extension of 37 days was noted for prostate cancer screening with prostate-specific antigen (blood) testing and 107 days with lung cancer screening using computed chest tomography, but these latter estimates were uncertain.
In conclusion, this analysis suggested that colorectal cancer screening with sigmoidoscopy may extend life by approximately 3 months; colonoscopy, however, was not included, and I suspect that procedure, after careful analysis, will save more lives than just noted. Lifetime gain for other screening tests appears to be quite limited or uncertain.
These findings suggest very minor gains in longevity, throwing into question the value of screening benefits in general, and whether they can justify the large costs involved. Screening can lead to many more people being negatively affected. i.e, requiring more testing and procedures, more false alarms and over-diagnoses, and being more likely to be subjected to excessive out-of-pocket payments or Medicare premiums. They also fail to take into account the potential anxiety arising from indeterminate or “false positive” results associated with such results.
Rather than extending efforts toward early detection, this kind of information suggests a greater need to apply the various early means to prevent cancers in the first place, such as avoiding cigarettes, proper diets and exercise, as others that I have pointed out in previous communications.
Obviously, we need more research to arrive at a definitive decision about screening.
Whether these screening tests are a good idea or not is actually a moving target. In any rate, stay tuned, while screening may not be such a good idea now, as new screening modalities emerge, the current ones may not be preferable any longer. Better testing, genetic or otherwise, might allow us to tailor screening more narrowly than the population-based approach we have now. Moreover, as treatment for cancer gets better, detecting cancer early may not be as important.