Three recent events highlight the extraordinary task that lies ahead for cancer prevention.
First: in late May, a World Health Organization panel added cellphones to a list of things that are "possibly carcinogenic" — a category that also includes pickles and coffee.
Second: in mid-June, the National Toxicology Program, countering years of lobbying by certain industries, finally classified formaldehyde (used in plywood manufacturing and embalming) as a carcinogen.
And third: in late June, the Food and Drug Administration issued newer and more graphic warning labels for cigarette packages. These include deliberately disturbing images of a patient with mouth cancer and of a man with tobacco smoke coming out of a tracheotomy stoma.
What connects these events? Together, they serve to remind us of three of the most potent challenges that cancer-control agencies face today. Indeed, it is essential to recognize these events as representing a progression: each corresponds to a crucial stage in the process of patrolling the borderlands of cancer. Effective cancer control depends on successful action at each of these complex stages.
The first challenge is scientific. It concerns the complexity of identifying new carcinogens, and the need for consistent standards for doing so. Take the purported link between cellphone radiation and brain cancer. This link is based largely on the so-called Interphone study. In Interphone, men and women with a variant of brain cancer (called glioma) were asked to recall their level of exposure to cellphone radiation. The results, at first glance, were provocative. Men and women who recalled moderate phone use seemed to havedecreased rates of brain cancer compared to those who rarely used cellphones. In contrast, men and women with the highest usage seemed to have an increased rate of brain cancer.
But pivotal uncertainties remain. Trials like Interphone depend on the ability of subjects to recall their prior exposures. Such recollections can be surprisingly inconsistent. Indeed, when some subjects' actual phone use was logged, there were broad discrepancies between actual and reported usage.
There are other difficulties. Despite a drastic increase in cellphone usage over the past decades, there has been no significant change in glioma cancer rates across the nation. Perhaps it is too early to judge, but the enormous increase in phone usage should have caused at least a minor blip in glioma rates over 20 years — but no such increase is apparent.
And finally, the kind of radiation emitted by cellphones — unlike the radiation emitted by X-rays or nuclear bombs — cannot directly damage DNA. X-rays and nuclear radiation possess the energy required to alter genes and thereby cause cancer. But the frequency of cellphone radiation is more than a million-fold lower. If cellphone radiation is causing cancer, it is doing so through a mechanism that defies our current understanding of carcinogenesis.
Brain cancer is a devastating illness, and it's worth being cautious, but the current data supporting the link between phone radiation and glioma are weak. The cellphone case is a reminder of how difficult it is to identify a new carcinogen — and how important it therefore is to have standards to make such classifications possible.
Discrepancies in standards for classifying carcinogens have led to confusion and turmoil in the public realm. In contrast to the World Health Organization, many agencies, including the National Cancer Institute, remain skeptical about the link between phone radiation and cancer, and are awaiting more definitive studies to clarify the issue. In part, the problem is semantic: the W.H.O.'s definition of "possibly carcinogenic" is much looser; coffee and pickles are included, even though the evidence for their carcinogenicity remains weak. But the split between the W.H.O. and other agencies on cellphones — emblematic of the split within the scientific community — has had the unfortunate effect of confounding the public, which now does not know which faction to believe.
The second challenge facing cancer control agencies is political. The formaldehyde case illustrates this. Unlike phone radiation, formaldehyde has a well-established mechanism to cause cancer: it is a strikingly reactive chemical that can directly attack DNA. Experiments performed in the 1970s demonstrated that the chemical causes cancer in mice and rats. Following this data, sophisticated trials showed that men and women exposed to formaldehyde — morticians, for instance — had higher rates of leukemia than unexposed people.
But some of these studies were performed three decades ago. Why have 30 years elapsed between them and the National Toxicology Program announcement? In part, because of active lobbying by various industries, in particular, plywood manufacturers, who have tried to thwart this classification.
Identifying a carcinogen, in short, isn't sufficient. Beyond the science — which, as the cellphone example shows, can be hard enough — cancer-control agencies need to bolster political support, and neutralize lobbying interests, before a culprit carcinogen can be revealed to the public.
The third challenge for the cancer community is social. The F.D.A.'s new labels on cigarette packages are a case in point. The human trials that established that tobacco smoke is a carcinogen were initially performed in the mid-1950s (some even earlier). The tobacco industry mounted an aggressive campaign to discredit the data, and continued marketing tobacco to the public. The landmark Surgeon General's Report on smoking and cancer was released in 1964. And it took yet another decade of innovative strategies, including powerful antitobacco advertisements and tort cases against tobacco companies, to alter the trajectory of smoking behavior in America.
But young men and women in some parts of the nation are smoking again: consumption in certain regions has been rising, and cancer rates will rise concomitantly. Evidently, identifying a carcinogen or advertising the risk to the public is not enough: cancer-control agencies need to invent and reinvent strategies continuously. Old warning labels generate habitual responses, so new, more disturbing labels are needed to invigorate attention.
Patrolling the world for real carcinogens, in short, is a complex task. Scientific challenges morph into political challenges that lead to social challenges. If reducing the incidence of cancer is a national goal — as it surely must be — then it is essential to recognize the many-dimensional nature of countering carcinogens.
