Linda at the humble log cottage built by Daniel Boone in his later years
That ponderous rag, the NY Times, has printed a very interesting
article on cancer statistics and how we
can use them to fool ourselves about progress in the War on Cancer. As you may already know, there are two “metrics”
to describe such progress: survival rate, and mortality rate. To illustrate: Survival rate in ovarian cancer is measured
by how many women are still alive five years
after diagnosis. This has increased from
roughly 33% in 1975 to 45% in 2010, a substantial gain, although in my opinion
pitifully inadequate. Mortality rate
over that period also improved, from 10 per 100,000 women to 8; also
progress. Although in this case the two
metrics yield similar results, in other cases they don’t. Here is why:
Mortality rate can be affected only by changes in such
factors as disease prevention and cure.
Survival rate, on the other hand, also is influenced by early
diagnosis. If early diagnosis doesn’t
contribute to more effective treatment, all it will do is inflate the survival
rate – without making a bit of difference in mortality. Conversely, if it leads to more effective
treatment – as is often the case – it will influence both survival and
mortality. The Times article givers a clear example involving a mythical malady
called thumb cancer. You should read it;
it will demystify cancer statistics to a degree. Here is the article:
This short essay was
brought to my attention by Dick Ingwall, who generously took time off from the
celebration of his 69th birthday to send it to me. Thanks, Dick: welcome to middle age.
Maybe some of you would be interested in a convenient source
of cancer statistics furnished us by the NCI.
Play around with this web site
As explained above, “Survival” means staying alive to a certain anniversary (often five years) after diagnosis; “cure” means becoming, and remaining, disease free. The new study (below) gives some robust statistics on survival to ten years, and they are encouraging. “Survival” will increase for several reasons: better therapy, earlier diagnosis, better data sets. “Cure” also depends on better therapy and better data, and leans very heavily on early diagnosis; catch it early enough and you can snuff it out, permanently – sometimes. In my book the most important statistic is “Mortality”; what fraction of the population dies of the disease. This depends on all of the above and, crucially, prevention. Mortality from lung cancer has shrunk dramatically in recent decades, not primarily from better treatment or earlier diagnosis, but from prevention. I wish there was such an uncomplicated way to prevent ovarian cancer, but I can’t think of one. Can you?
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There likely is an uncomplicated solution: healthy diets and lifestyles. The more we can promote this, especially in schools, the better.
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