Recently, the BMJ published a manuscript on people's willingness to accept overdetection in cancer screening:
Objectives To describe the level of overdetection people would find acceptable in screening for breast, prostate, and bowel cancer and whether acceptability is influenced by the magnitude of the benefit from screening and the cancer specific harms from overdetection.
Design Online survey. Women were presented with scenarios on breast and bowel cancer, men with scenarios on prostate and bowel cancer. For each particular cancer, we presented epidemiological information and described the treatment and its consequences. Secondly, we presented two different scenarios of benefit: one indicating a 10% reduction in cancer specific mortality and the second indicating a 50% reduction.
Setting Online survey of the population in the United Kingdom.
Participants Respondents were part of an existing panel of people who volunteer for online research and were invited by email or online marketing. We recruited 1000 respondents, representative for age and sex for the UK population.
Main outcome measures Number of cases of overdetection people were willing to accept, ranging from 0-1000 (complete screened population) for each cancer modality and each scenario of benefit.
Overdetection is the most serious adverse effect of cancer screening. It refers to the pickup and diagnosis of a disease that otherwise would never have caused any problems and remained largely undiagnosed. It leads to significant health care spending, and possible mental and physical health consequences.
In recent years, more and more focus (and blog posts) have discussed overdetection, and how its presence as a harm might overwhelm benefits from screening. But most of those concerns are raised at a population level. Little has been known about actual patient's feelings on the subject.
This study surveyed 1000 people in the UK to determine what level of overdetection people would accept in order to think a screening program was beneficial. Two different scenarios were presented. In the first, screening resulted in a 50% relative reduction in cancer mortality. Specifically, without screening, if 1000 people were screened, 50 would be diagnosed with cancer, and 10 would die. Screening would reduce this to 5. In the second scenario, screening resulted in a 10% relative reduction in cancer mortality. Specifically, without screening, if 1000 people were screened, 50 would be diagnosed with cancer, and 10 would die. Screening would reduce this to 9.
So in the better scenario, screening would save 5 lives out of 1,000 screened. In the worse scenario, screening would save 1 life out of 1,000. And then they asked respondents how many cases of overdetection they would accept, given that this can lead to downstream negative consequences.
In 1,000 people screened, the medians ranged from 113 cases of overdetection tolerable to save one life to 313 cases of overdetection tolerable to save 5 lives.
The USPSTF recently posted modifications to their breast cancer screening recommendations for public comments. The accompanying data report stated that RCT evidence shows that about 20% of women diagnosed with breast cancer are cases of overdetection. These numbers would be much, much less than what the median patient seems willing to tolerate.
To be perfectly honest, I was surprised. I think overdetection is a huge problem, and I think 20% of cases being overdiagnosis is a big deal. Apparently, I'm in the minority. I'm not the extreme, though. Depending on the scenario, about 4-7% of people would accept no overdetection at all.
Between 7-14% of people thought that it would be acceptable for the entire screened population to be overdetected (and go through treatment, I suppose) to save at least one life.
The point I'd take from this is that people seem willing to accept widely varied amounts of "harms" to potentially save a life. If that's the case, then the value of screening should be widely varied to patients as well. If that is the situation, then patients and doctors should likely decide for themselves if screening is appropriate for them. Appropriately, that's what the USPSTF recommended, for women age 40-49 with respect to breast cancer.
One final note. The study showed we don't talk about this enough. Less than 30% of respondents had heard of overdetection before this study. Patients can only make informed decisions if they are actually informed.