Wednesday, April 8, 2015

Cancer mortality vs survival rates

Overdiagnosis of cancer greatly impacts the survival rates. Overdiagnosis occurs when people are told they need treatment for a cancer which will never progress or isn't even cancer (but we really hope that it really is cancer). If your cancer is never going to kill you, you don't need the treatment. And the treatment can cause you harm.

"Overdiagnosis can have a powerful effect on survival rates, even if no one has their life prolonged.
To understand why, imagine a country in which 1,000 people are found to have Cancer X because of symptoms (they all have progressive cancer). Five years after diagnosis, 500 are alive — producing a five-year survival rate of 500/1000 or 50 percent — and 500 have died.

Now imagine the same country with lots of cancer screening and/or incidental cancer detection.  Perhaps 2,000 would be given a diagnosis of Cancer X, although 1,000 would actually have indolent forms and not be destined to die from their cancer.  Five-year survival will increase dramatically, to 75 percent, because the 1,000 people with indolent cancer appear in both parts of the fraction: 1,500/2,000.  But what has changed?  Some people have been unnecessarily told they have cancer (and may have experienced the harms of therapy), and the same number of people (500) still died from Cancer X."

Got it? Good. And this over diagnosis costs billions. And the stress is horrible on the people. And unnecessary cancer treatment, which is pretty harsh, can cause people long term health concerns.

So when people run around saying "all these advances from research your donations helped fund have helped reduce the survival rates from this cancer", don't accept them at face value. Real research is needed to help prevent overdiagnosis and mortality rates are what need the real review.

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