Does cancer screening save lives? On the eve of Pink October, the question may seem inappropriate. But that’s the question researchers at the University of Oslo’s Institute of Health and Society are asking in a major study¹ published in late August by JAMA Internal Medicine: To what extent is cancer screening promoted to save costs? life, does this increase life expectancy?
Analyzing 18 randomized clinical trials (2.1 million people with a follow-up period of more than 9 years), the authors of this meta-analysis estimated the life expectancy obtained from screening tests for colorectal cancer (sigmoidoscopy, colonoscopy, stool test), lung cancer (computed tomography), prostate cancer (PSA analysis) and breast (mammography). The results obtained by comparing screening and no screening are disconcerting: an increase in life expectancy is not clearly demonstrated for five of the six commonly used screening tests.
According to this publication, only colorectal cancer screening with sigmoidoscopy “significantly” increased survival (by 110 days) in the studies. “No statistically significant results” for mammography screening (breast cancer) and stool occult blood testing (colorectal cancer). Regarding colonoscopy screening for colorectal cancer, prostate cancer, and lung cancer, estimates of life expectancy gains are “uncertain.”
For some, screening prolongs life. Other times it shortens it.
How can these results be explained? Unlike most studies in which the benefit of screening is assessed by measuring only cancer mortality (with and without screening), in this meta-analysis the authors isolated overall mortality (all causes combined). screening procedures and treatment-related complications. “Some people prolong their lives thanks to these screening tests: cancer is detected at an early stage, and they survive the screening and treatment without damage or complications. However, other people have their lives shortened because of screening. This loss of life expectancy is caused by harm associated with screening or treatment of detected cancers. For example, due to perforation of the colon during colonoscopy or myocardial infarction after radical prostatectomy,” the authors of the publication explain.
And he added: “A cancer diagnosis can also lead to additional non-cancer deaths from suicide, cardiovascular disease or accidents. Moreover, increased surveillance after cancer screening may increase the risk of other incident diseases that would not have been detected in the absence of screening. »
Overdiagnosis: an underestimated risk
In other words, this meta-analysis shows that overall mortality is the same with or without screening. Mortality from causes other than cancer associated with screening may negatively offset the potential benefits of population screening. The authors of the publication also emphasize that most studies underestimate the main risk of screening: overdiagnosis. This involves identifying non-progressive cancers that, if not detected, would never impact a person’s life and therefore would never be treated. “Although our meta-analysis shows that claims that screening saves lives are not supported by the best available evidence, we do not advocate eliminating all screening,” conclude the researchers, who believe it might be “more prudent to reconsider priorities public health and objectively inform interested people about the advantages and disadvantages of screening.”
“Doctors believed that breast cancer screening would increase life expectancy, especially for me. Today this enthusiasm has faded. When we take into account all the lethal consequences caused by cancer detection as a result of screening, the best examples of which are prostate and breast diseases, we can no longer say that it saves the population,” reacts Dr. Cecile Boer, radiologist and president of Cancer. Rose,” a group of doctors who lament that “women are still not being given honest and complete information about the harms of breast cancer screening.”
Participating in breast cancer screening can be beneficial, but for whom? It’s a lottery!
Cecile Boer, radiologist
In response to the “marketing campaigns” of Pink October, the association’s information website has been publishing and popularizing international data and independent research on this topic since 2015. The radiologist continues: “There may be benefits from participating in breast cancer screening. but for whom? It’s a lottery! When we look at the work of the Cochrane researchers, we see that we need to screen 600,000 patients over ten years before we can say that for every 2,000 women screened, we save one life. In exchange for this life saved, 200 women were distressed by a false alarm, many of whom were given unnecessary biopsies, and 10 were overdiagnosed, at least one of whom died from the effects of treatment.
The risk of dying from breast cancer has been declining since the 1990s, regardless of whether people are screened or not.
Citing “another important study” published in June 2023 in the British Medical Journal, the radiologist explains that the risk of death from breast cancer has been falling since the 1990s, regardless of screening or lack thereof, “likely due to treatment and prevention.” campaigns.
As a radiologist today, it is critical that medical information evolves. “We will not stop breast cancer screening. It is ingrained in our society, although it requires huge costs for very little benefit. Instead of forcing women to participate in screening, let’s inform them honestly about the risks they face so they can make an informed choice. »
¹Life expectancy derived from cancer screening tests: a meta-analysis of randomized clinical trials
² Breast cancer mortality in 500 000 women with early invasive breast cancer diagnosed in England, 1993–2015: a population-based observational cohort study