The Pump Handle, February 5, 2007
DROP IN CANCER DEATHS HYPE -- WHAT'S BEHIND THE NUMBERS?
[Rachel's introduction: Deaths from cancer have dropped slightly for the past two years, as more people have quit smoking. Does this bit of good news mean the cancer epidemic is over? Hardly.]
By Dick Clapp
Late last month, there was a series of news stories about the drop in cancer deaths reported in 2004 as compared to 2003. The Washington Post story ran under the headline "Cancer Deaths Decline for Second Straight Year," and the New York Times headline read "Second Drop in Cancer Deaths Could Point to a Trend, Researchers Say." President George W. Bush was quoted as saying "This drop was the steepest ever recorded... Progress is being made." What he did not say was that a drop in cancer deaths has been recorded in only two years since the data have been collected -- and this drop was greater than the one the previous year, 2003 compared to 2002. Both stories noted that the decline was small in absolute numbers (3,014 fewer deaths due to cancer in 2004 compared to 2003), but neither pointed out that cancer incidence has been either slightly increasing (females) or flat (males) in the past decade.
The drop in cancer deaths from 556,902 in 2003 to 553,888 in 2004 represents a one half of one percent drop. The National Center for Health Statistics report (see Table 2 in particular) actually reported some other findings that are more important than the drop in cancer deaths, in terms of public health. For example, there were 50,673 fewer deaths from all causes in 2004 than in 2003, and the drop in heart disease deaths was much greater than for cancer. The drop in deaths due to cerebrovascular disease (strokes), chronic lower respiratory disease, influenza and pneumonia, septicemia, hypertension and diabetes were all greater in percent decline than the drop in cancer deaths. In fact, many of these causes of death are related to the same risk factors (smoking, obesity, lack of exercise, access to health care) that the news accounts say were the reason for the decline in cancer deaths. The question then becomes, why are these other diseases declining more than cancer. The headlines might have been, "Cancer lags behind other diseases in decline from 2003 to 2004."
One other missing aspect of the cancer stories is what is sometimes called the cancer burden, or the number of people diagnosed and living with the disease. Needless to say, it's better to be alive, considering the alternative, but the economic and psychological burden on families of cancer patients can be enormous. So, while age-adjusted cancer incidence rates have been slightly increasing in females and essentially staying flat in males over the last decade (see SEER Program data) and mortality rates have been declining, this means the number of people living with cancer (the burden) has been getting steadily larger. The real goal from a public health point of view, is to reduce the incidence of cancer by prevention programs. Probably the best news in the past decade in this regard has been the declining lung cancer rate in males -- which has mostly been due to declining prevalence of cigarette smoke exposure, both to smokers and those around them. The incidence of this cancer has not declined because of better screening or treatment, but because of primary prevention.
Another piece of the cancer story has to do with childhood cancer incidence and mortality. Cancer is, thankfully, a rare illness in children, and mortality rates have gone down for many childhood cancers over the past two decades. Childhood cancer incidence has been steadily going up, however, and this cannot be due to some of the factors cited in adults (smoking, obesity, lack of exercise, etc.). It's also not that genetic susceptibility is increasing in children because heritable factors would not be likely to change in one generation. Here, most people would gladly accept the burden of keeping a child alive who has been diagnosed with cancer. But wouldn't we all rather that the children not be getting cancer in the first place? The explanation for the steady increase in childhood cancer incidence is not at hand, but at least one place to look is prenatal and early childhood environmental carcinogenic exposures. A report by Tami Gouveia-Vigeant and Joel Tickner published by the University of Massachusetts's Lowell Center for Sustainable Production (PDF summary here; PDF report here) finds that "evidence increasingly indicates that parental and childhood exposures to certain toxic chemicals including solvents, pesticides, petrochemicals and certain industrial by-products (dioxins and polycyclic aromatic hydrocarbons) can result in childhood cancer."
In any event, the recent flurry of headlines about the decline in cancer deaths seems to be more wishful thinking and political spin than a sober look at what's behind the numbers. We'll be saying more about this in coming months.
Dick Clapp is a professor at Boston University School of Public Health, a member of the Scientific Knowledge and Public Policy Planning Committee, and Co-Chair of Greater Boston Physicians for Social Responsibility. He was Director of the Massachusetts Cancer Registry from 1980-1989 and has been involved in numerous cancer cluster investigations.