Saturday, October 25, 2008

U.S. Cancer Death Rates: The Crude Reality

There is a rising sense that, thanks to modern medical therapies, we are finally beginning to win the War on Cancer (officially begun under President Nixon, in 1971). Since 1991, the age-adjusted rate of cancer deaths in the U.S. has been dropping. If you simply look at the graphed trend, you might assume that we can eradicate cancer in one or two more generations.

Here is the age-adjusted cancer death rate, in the U.S. for the period 1969 to 2005.

Well, reality is not exactly as it seems. First off, the data is age-adjusted. Age-adjustment is a legitimate precedure, performed by statisticians who are comparing disease rates in different populations (or in one general population at different times in history). Age-adjustment normalizes changes in disease rated caused entirely by shifts in the ages of people in the population. If a disease exclusively strikes people over the age of 60, and the population has a large increase in the over-60 population, then it would necessarily have an increase in the incidence of disease, on this basis, even when there are no medical or biological causes for the increase. To rectify this effect, statisticians "adjust" the data to normalize the distribution of ages against a standard age distribution (now, the year 2000 age distribution determined by the U.S. Census bureau).

If you want to know the impact of a disease on a population, you need to use the crude data, not the age-adjusted data (because the impact of a disease on healthcare resources and on society cannot be sensibly "adjusted").

Here is a graph of the crude death rate data for all cancers, in the United States, between 1969 and 2005

The rate of deaths per hundred thousand population, is getting worse and worse, despite a relative respite in the past decade or so.

Now, if you want to know the true burden of cancer on the population, you need to look at the total number of people dying from cancer (not the rate of cancer deaths). To find the total number of deaths from cancer, you multiply the crude death rate for each year, by the population of the U.S. during that year (obtained from the U.S. Census bureau), expressed as 100s of thousands.

Here is is the total number of cancer deaths, in the U.S. for each year from 1969-2005.

The number of people dying from cancer, in the U.S., just gets higher and higher. Again, towards the end of the graph, there are a few years where there the total number of deaths seems to have leveled off or even improved slightly.

I hope to discuss, in much more detail in a future blog, how these graphs were generated directly (the first two graphs) or indirectly (the third graph) from the NCI's SEER (National Cancer Institute's Surveillance Epidemilogy and End Results) database.

What is going on at the tail end of the graph? Is this leveling of cancer deaths due to improved treatments for cancer? We'll discuss this in a future blog.

- © 2008 Jules Berman

key words: neoplasms, cancers, tumor, tumour, epidemiology, cancer rates, cancer news, cancer trends

In June, 2014, my book, entitled Rare Diseases and Orphan Drugs: Keys to Understanding and Treating the Common Diseases was published by Elsevier. The book builds the argument that our best chance of curing the common diseases will come from studying and curing the rare diseases.

I urge you to read more about my book. There's a generous preview of the book at the Google Books site. If you like the book, please request your librarian to purchase a copy of this book for your library or reading room.