By Brian Carnell

Friday, January 5, 2001

George Monbiot thinks the United States is awash with cancer and is certain he knows the responsible parties -- evil corporations and their synthetic chemicals. Unfortunately Monbiot doesn't seem to actually know much about the cancers he writes about.

It is widely believed, for example, that the increase in cancer incidence is due primarily (though not exclusively) to a small number of factors. First, many cancers strike older people disproportionately, and since people live longer than ever it shouldn't surprise anyone that cancer incidence is rising. Second, there are more sophisticated tests available for diagnosing cancer, which inevitably leads to higher rates. Other behavioral factors such as the horrible level of obesity in the United States might play a role as well, but at the moment that is just speculation.

Monbiot will not hear of this explanation,

These increases are often ascribed to better detection and an ageing population. But the figures are age-adjusted: a 60-year-old today is 200% more likely to contract prostate cancer than a 60-year-old would have been in 1950. Reported cancers have continued to rise after the universal deployment of new screening techniques: this is not an artefact of diagnosis. Cancer is thriving.

Monbiot chose very poorly in picking prostate cancer, since the increase in prostate cancer is almost entirely due to new screening techniques which even the most scientifically-challenged person would discover with a basic literature search of prostate cancer studies.

Prostate cancer is a disease that has seen a number of innovations in detection since 1950 that have caused reported incident rates to ramp up dramatically. For example from 1989 to 1992, prostate cancer incidence rose 69 percent. Was there a massive nationwide exposure to dangerous chemicals in those years? Nope. Rather a blood test that looks for the prostate specific antigen was introduced and became widely used beginning in the late 1980s

What Monbiot doesn't bother to report is that since 1992, prostate cancer rates have been declining. From 1973 to 1990, prostate cancer incidence increased 3.4 percent per year, but from 1990 to 1995 it decreased 1.0 percent each year. Did something happen in the 1990s to lower prostate cancer incidence? Nope. Instead it's a common effect that occurs with the availability of a new screening test. Initially as news of the new test spreads, the number of people receiving the test spikes upward very quickly. After a few years, the number of people receiving the test for the first time starts falling, as does the incidence rate.

It is this sort of phenomenon which belies Monbiot's claim that "reported cancers have continued to rise after the universal deployment of new screening techniques." There simply is no such thing as a "universal deployment" of a new screening techniques. No population is ever universally tested using a specific cancer screening technique, and factors such as general society awareness of the disease, differing patterns of use of new screening techniques, etc., can all influence incidence rates (I don't have hard data to support this, but I would wager that a much higher percentage of people over the age of 60 receive some form of prostate cancer screening than did in the 1950s, for example).

Meanwhile, survival rates for prostate cancer have increased dramatically. In 1954, the five year survival rate for men diagnosed with prostate cancer was only 43 percent. In 1995 it was 93 percent (although there is still a lot of heated debate over what is being measured by five year survival rates, and it is unclear that prostate cancer treatments are actually prolonging life expectancies of those with prostate cancer).

Sources:

Purporting to be beating cancer. George Monbiot, The Guardian of London, January 4, 2001.

Recent Trends in Prostate Cancer Incidence and Mortality. National Institutes of Health, Press Release, November 21, 1997.

Cancer Incidence and Mortality, 1973-1995, A Report for the U.S. National Institutes of Health, Press Release, March 12, 1998.

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