We receive constant messages about the importance of cancer screening for early detection to improve our chances of survival. We hear the horror stories about the person who didn’t get checked until it was too late, and his or her cancer was already so advanced that treatment was ineffective.
But when we hear about the percentage reduction in deaths of a particular cancer or the increase in 5-year survival rates, what do those numbers actually mean? Just as a refresher, here is the rate of death from cancer over the last 120 years and the results of tens, if not hundreds, of billions of dollars invested into the advanced cancer screening and treatments over the last 50 years.
Mortality data sources: https://www.cdc.gov/nchs/products/vsus.htm & https://wonder.cdc.gov/Deaths-by-Underlying-Cause.html
Per my usual disclaimer, I am not a doctor or expert in anything much less medicine and cancer. I am not offering advice or making recommendations. I am simply sharing information that is available to the public, but which for reasons we’ll explore later, the medical community is reticent to share with their patients.
I have been reading “Risk Savvy” by Gerd Gigerenzer which is where I uncovered much of the information I’m sharing in this post. Gigerenzer is a German psychologist and is currently director of the Harding Center for Risk Literacy and is former director of the Center for Adaptive Behavior and Cognition at the Max Planck Institute for Human Development and at the Max Planck Institute for Psychological Research in Munich in addition to many other esteemed positions.
I highly recommend reading this book specifically to understand the literal marketing games being played by the medical industry. This book will help you better understand how to determine true risks and benefits, and will allow you to make more informed decisions regarding the healthcare options you choose to pursue.
Back to the original question. What does it mean when we hear we can reduce cancer deaths by X% with early detection and treatment, or increase 5-year survival rates Y%?
While prevention is key when it comes to avoiding death from cancer, early detection is not prevention - it’s simply finding cancer that already exists. And in reality, everyone has some cancer at any given time in their bodies. But not all cancers progress and become problematic.
Let’s explore what a positive result from a cancer screen means and what the impacts are on 5-year survival rates, and more importantly, mortality.
Prostate Cancer
Prostate Specific Antigen (PSA) tests are often used to identify cancer of the prostate. But according to the scientific data, these tests have incredibly minimal, if any, impact on mortality rates.
For example, this meta-analysis published in the British Medical Journal found no significant effect from screening on death from prostate cancer or all-cause mortality.
Another study on screening and the reduction of metastatic disease published in European Urology found a relative risk reduction of 42% in men who were screened. But the absolute risk reduction was an unimpressive 0.31% or 3.1 per fewer cases of metastatic disease per 1,000 men screened.
A follow up study on prostate screening and mortality published in the Lancet found that the absolute risk reduction of death from prostate cancer as a result of screening was 1.28 per 1,000 men or 0.128%. Essentially 1 man’s life is saved from prostate cancer for every 781 men screened.
So how does the sick care establishment claim that screening increases 5-year survival rates by 80%+? Men in the US are encouraged to start screening for prostate cancer at the age of 50 so cancers are identified earlier than if one were to wait for symptoms to arise. This is called lead time bias.
I’m stealing an example from “Risk Savvy” here. Say we have a group of 100 men who don’t get screened and get a cancer diagnosis at 67 years of age and they all die at the age of 70. Then we have another group of 100 men who do get screened and get a cancer diagnosis at 60 years of age but also die at 70. The second group has a 100% 5-year survival rate whereas the first group that didn’t get screened has a 0% 5-year survival rate even though they all die at the same age!
5-year survival rates and relative risk reduction actually mean very little whereas absolute risk reduction and all-cause mortality mean a great deal. As we can see from the data, absolute risk reduction and mortality reduction from screening is not much above zero on absolute terms.
The other problem with screening is overdiagnosis and false positives. The actual lifetime risk for a man dying of prostate cancer is only about 3%. The median age of death from prostate cancer is 80 years with two thirds of all prostate cancers deaths older than 75 years.
Most men, if they live long enough, develop non-progressive prostate cancer that will never cause any significant problems. But thousands of men die within one month of surgery and several times more will be left with incontinence and erectile dysfunction for little if any real benefit.
The following charts are excellent simple representations that help a person better understand risk:
Source: https://www.researchgate.net/publication/224897251_Psychological_Research_and_the_Prostate-Cancer_Screening_Controversy
Breast Cancer
Continued in Part 2…