Thursday, July 10, 2008

Neoplasms: 3

This is the third blog in a series of blogs on neoplasia.

As shown in yesterday's blog, the death rate from cancer in the U.S. is about the same today as it was in 1950 and 1978.

The cancer death rate is the number of deaths from cancer (per 100,000 age-adjusted population). The cancer death rate is very different from the cancer survival rate. The cancer survival rate is determined by the number of people who have cancer and who do not die from the cancer (in some pre-determined observation period).

The cancer death rate is affected by factors that have nothing to do with cancer treatment. For example, if the incidence of a major cancer were to drop (as in the case of lung cancer in certain subpopulations), this might reduce the cancer death rate, even if it were not accompanied by improved methods of lung cancer treatment. Likewise, if the population started to die off from some cause other than cancer (e.g., a major influenza outbreat), the cancer death rate might drop. We'll discuss some of the limitations of the cancer death rate in a future blog. Still, as a rough indicator, the cancer death rate serves an important purpose. The U.S. cancer death rate has barely budged in over 50 years, and this tells us that we are not winning the war against cancer.

In the past year, I've noticed that cancer journalists like to point out that the cancer death rate has been steadily dropping since the early 1990s. This is true, but the importance of this trend is small.

Let's look at the year-by-year cancer death rate from NCI's Surveillance Epidemiology and End Results project, available at:

Year Adjusted cancer death rate per 100,000
1975 199.1
1976 202.3
1977 203.0
1978 204.4
1979 204.5
1980 207.0
1981 206.4
1982 208.3
1983 209.2
1984 210.9
1985 211.3
1986 211.8
1987 211.9
1988 212.6
1989 214.3
1990 214.9
1991 215.1
1992 213.5
1993 213.4
1994 211.7
1995 209.9
1996 207.0
1997 203.6
1998 200.8
1999 200.7
2000 198.7
2001 195.9
2002 193.7
2003 190.0
2004 185.8
2005 184.0

The cancer death rate has been dropping since 1991, but only after a small rise in the cancer death rate from 1975 to 1991. Basically, we have about the same cancer death rate today as we had in 1975. Nobody can say, with any certainty, why we had that bump in the U.S. cancer death rate between 1975 and 2005. But cancer researchers did not take credit for the rise in cancer prior to 1991. Likewise, cancer researchers cannot take credit for the drop in cancer after 1991.

All we can say with any confidence is that our progress against cancer has not yielded any major changes in the U.S. cancer death rate.

What is the significance of the cancer survival rate, and what can say about our ability to successfully treat people who develop cancer? That will be the subject of the next few blogs.

-Copyright (C) 2008 Jules J. Berman

key words: cancer, tumor, tumour, carcinogen, neoplasia, neoplastic development, classification, biomedical informatics, tumor development, precancer, benign tumor, ontology, classification, developmental lineage classification and taxonomy of neoplasms

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