> Specifically, the U.S. has the best cancer survival rates in the world.
This is a misunderstanding of what "5 year survival rate" means. You're missing "lead time bias", and "over diagnosis bias".
From Risk Savvy by Gerd Gigerenzer
--begin quote
While running for president of the United States, former New York City mayor Rudy Giuliani said in a 2007 campaign advertisement:1
"I had prostate cancer, 5, 6 years ago. My chance of surviving prostate cancer—and thank God, I was cured of it—in the United States? Eighty-two percent. My chance of surviving prostate cancer in England? Only 44 percent under socialized medicine."
For Giuliani, this meant that he was lucky to be living in New York and not in York, since his chances of surviving prostate cancer appeared to be twice as high. That was big news. It was also a big mistake. Despite the impressive difference in survival rates, the percentage of men who died of prostate cancer was about the same in the United States and the UK.2 How can survival be so different when mortality is the same?
The answer is that when it comes to screening, differences in survival rates don’t tell us anything about differences in mortality rates. In fact, over the past fifty years, changes in five-year survival for the most common solid tumors had no connection with changes in mortality.3 There are two reasons.
How Rudy Giuliani Was Misled
The first reason is called lead time bias. Imagine two groups of men with invasive prostate cancer. The first consists of men in Britain, where screening for prostate-specific antigens (PSA) is not routinely used and most cancer is diagnosed by symptoms. The second group is made up of men in the United States, where routine use of the test began in the late 1980s and spread rapidly, despite the lack of evidence that it saves lives.
In the British group, prostate cancer is detected by symptoms, say at age sixty-seven (Figure 10-1 top). All of these men die at age seventy. Everyone survived only three years, so the five-year survival is 0 percent. In the U.S. group, prostate cancer is detected early by PSA tests, say at age sixty, but they too die at age seventy (Figure 10-1 bottom). According to the statistics, everyone in that group survived ten years and thus their five-year survival rate is 100 percent. The survival rate has improved dramatically, although nothing has changed about the time of death: Whether diagnosed at age sixty-seven or at age sixty, all patients die at age seventy. Survival rates are inflated by setting the time of diagnosis earlier. Contrary to what many people have been told, there is no evidence that early detection and subsequent treatment of prostate cancer prolongs or saves lives.
The second reason why survival rates tell us nothing about living longer is overdiagnosis bias. Overdiagnosis happens when doctors detect abnormalities that will not cause symptoms or early death. For instance, a patient might correctly be diagnosed with cancer but because the cancer develops so slowly, the patient would never have noticed it in his lifetime. These cancers are called slow-growing or nonprogressive cancers.4 PSA screening detects both progressive and nonprogressive cancers but, like most other cancer screening tests, cannot tell the difference between them. Figure 10-2 (top) shows 1,000 British men with progressive cancer who do not undergo screening. After five years, 440 are still alive, which results in a survival rate of 44 percent. Figure 10-2 (bottom) shows 1,000 Americans who participate in PSA screening and have progressive cancer. The test, however, also finds 2,000 people with nonprogressive cancers—meaning that they will not die from them. By adding these 2,000 to the 440 who survived progressive cancer, the survival rate leaps to 81 percent. Even though the survival rate increases dramatically, the number of men who die remains exactly the same.
Funny thing: in my job, I've calculated the relative survival rate of prostate cancer (the difference in mortality risk between people diagnosed and a similar population in age, sex, and race). Cause of death is not considered, only that there was a diagnosis (avoids complicate deaths and captures indirect influence). It'll often be that men diagnosed with prostate cancer have a better 5-year survival rate than men who did not receive a diagnosis. And that's after excluding non-invasive tumors.
Why? No definite idea right now. Possible correlation: a diagnosis happens when a man actively cares about his health (regularly brings up troubles with his primary care physician, asks for screening tests), which also implies he has the money to do so. This is also bolstered by the fact the survival stats don't include diagnoses at time of death. So it misses the guys who never got tested before it killed them.
By the way, if you look up the relative survival stats on the CDC's website, they won't show anything above 100% relative survival. Im short, they never let the added risk of death go below zero. Which is dumb, in my opinion. It's editing data because it violates the assumption the model is perfect.
Does this correlation still hold if you look at men below a certain age? Since prostate cancer increases with age then you could get a bias towards the more healthy as the non-prostate cancer peers die earlier of some others cause.
I can't answer that until tomorrow (vacation). We try to reduce bias from competing causes of death by using the Pohar Perme method [0].
Though I now wonder if there is a larger difference for prostate cancer than other cancer types. It's commonly believed by cancer researchers that, if they autopsied everyone, they would find a prostate tumor in most men over 65.
Thank you for sharing this quote, I learned about this a long time ago and have been looking for a compelling way to make the case. People are often surprised at how ineffective early and frequent screenings can be -- depending on the disease of course. The risk of unnecessary exploratory surgery and other adverse effects of a false positive can actually add to aggregate patient risk, not reduce it.
One of my mentors was recently diagnosed with prostate cancer due to an elevated PSA test. He is 76 years old. No symptoms. His father died of prostate cancer at the age of 96. The doctors scared him into treatment (the ol' if you don't do this you might die trick) and proceeded to irradiate his abdomen damaging his nerves and causing his legs to atrophe and his outcome on life to plummet. He's just now getting around to realizing that the doctors are the ones that hurt him and he has no intention of listening to them again.
This is a misunderstanding of what "5 year survival rate" means. You're missing "lead time bias", and "over diagnosis bias".
From Risk Savvy by Gerd Gigerenzer
--begin quote
While running for president of the United States, former New York City mayor Rudy Giuliani said in a 2007 campaign advertisement:1
"I had prostate cancer, 5, 6 years ago. My chance of surviving prostate cancer—and thank God, I was cured of it—in the United States? Eighty-two percent. My chance of surviving prostate cancer in England? Only 44 percent under socialized medicine."
For Giuliani, this meant that he was lucky to be living in New York and not in York, since his chances of surviving prostate cancer appeared to be twice as high. That was big news. It was also a big mistake. Despite the impressive difference in survival rates, the percentage of men who died of prostate cancer was about the same in the United States and the UK.2 How can survival be so different when mortality is the same?
The answer is that when it comes to screening, differences in survival rates don’t tell us anything about differences in mortality rates. In fact, over the past fifty years, changes in five-year survival for the most common solid tumors had no connection with changes in mortality.3 There are two reasons.
How Rudy Giuliani Was Misled
The first reason is called lead time bias. Imagine two groups of men with invasive prostate cancer. The first consists of men in Britain, where screening for prostate-specific antigens (PSA) is not routinely used and most cancer is diagnosed by symptoms. The second group is made up of men in the United States, where routine use of the test began in the late 1980s and spread rapidly, despite the lack of evidence that it saves lives.
In the British group, prostate cancer is detected by symptoms, say at age sixty-seven (Figure 10-1 top). All of these men die at age seventy. Everyone survived only three years, so the five-year survival is 0 percent. In the U.S. group, prostate cancer is detected early by PSA tests, say at age sixty, but they too die at age seventy (Figure 10-1 bottom). According to the statistics, everyone in that group survived ten years and thus their five-year survival rate is 100 percent. The survival rate has improved dramatically, although nothing has changed about the time of death: Whether diagnosed at age sixty-seven or at age sixty, all patients die at age seventy. Survival rates are inflated by setting the time of diagnosis earlier. Contrary to what many people have been told, there is no evidence that early detection and subsequent treatment of prostate cancer prolongs or saves lives.
The second reason why survival rates tell us nothing about living longer is overdiagnosis bias. Overdiagnosis happens when doctors detect abnormalities that will not cause symptoms or early death. For instance, a patient might correctly be diagnosed with cancer but because the cancer develops so slowly, the patient would never have noticed it in his lifetime. These cancers are called slow-growing or nonprogressive cancers.4 PSA screening detects both progressive and nonprogressive cancers but, like most other cancer screening tests, cannot tell the difference between them. Figure 10-2 (top) shows 1,000 British men with progressive cancer who do not undergo screening. After five years, 440 are still alive, which results in a survival rate of 44 percent. Figure 10-2 (bottom) shows 1,000 Americans who participate in PSA screening and have progressive cancer. The test, however, also finds 2,000 people with nonprogressive cancers—meaning that they will not die from them. By adding these 2,000 to the 440 who survived progressive cancer, the survival rate leaps to 81 percent. Even though the survival rate increases dramatically, the number of men who die remains exactly the same.