15 June 2013

The media and risk communication: the case of liver cancer

The incidence of liver cancer in Canada has tripled since the 1970s. If this headline-style statistic causes anxiety, the media may have achieved their goal in a recent spate of news stories.

The CBC and other sources cite a recent report published by The Canadian Cancer Society, Statistics Canada and the Public Health Agency of Canada. The report points out that the incidence of non-metastatic liver cancer has increased substantially since the 1970s as a result of the changing occurrence of known risk factors, notably infection by hepatitis B virus (HBV) or hepatitis C virus (HCV), but also alcoholism, aflatoxin exposure and others.

This is interesting from the perspective of public health managers: if liver cancer rates continue to rise, certain population-level interventions may become worthwhile, for example, screening for HBV and HCV.

However, it is not interesting from the perspective of individual decision-making, because increased rates of liver cancer are explained by known risk factors. Regardless of population-level changes that have caused the incidence to rise, an individual's risk of liver cancer remains the same for a given exposure to environmental and genetic risk factors. In fact, the same report shows that the five-year survival ratio (fraction of cases still alive after five years) nearly doubled between 1992 and 2003, which justifies optimism about the prospects for individuals affected.

News articles mention the risk factors for liver cancer but do not make explicit that the rise in cancer follows from changes in the prevalence of these risk factors that are not in themselves news. The media portray the increase in cancer rates with a tone that would fit better a surge in property crimes or terrorism. Indeed, the very frame of a news article anticipates some response on an individual level; in this case, however, the reader seems left to guess what an appropriate reaction might be.

Wilkins and Patterson have written about this precise phenomenon, noting that the news media treat risk situations "as novelties, failing to analyze the entire system, and using insufficiently analytical language". Some scholars (e.g., TF Saarinen) argue, as I do here, that the media have a responsibility to put news on risk statistics into some larger context . Others (e.g., S Dunwoody) contend that media efforts in this direction have not been successful, and that the media should refrain from adding commentary or providing instruction. However, when news reports on risk statistics do not include any context, commentary or instruction, it is far easier to indulge in sensationalism. Indeed, Wilkins and Patterson note that 'a journalist's definition of a good news story means a catastrophe for someone else.'

Reader comments on the liver cancer story show how the public reach for explanations obviously bound up in their own worldview and preconceptions when faced with such a lack of context (see samples below, copied from the CBC story linked to above). In this sense, the news seems to self-sensationalize; it is not necessary for the media to exaggerate the story, but merely to present it without context.

The tendency for people to selectively retain information that confirms their preconceptions is well referenced. So is the public's tendency to overestimate cancer risk, especially as compared to other chronic diseases. The public are notoriously blasé with respect to their perception of disease risk, but cancer has a mythology that often reflects deeper skepticism and resentment of technological advance and a scientistic culture. These factors combine to make cancer risk communication a uniquely sensitive topic in terms of media treatment.

Reader comments range from muddled remarks on increased exposure to 'toxins' to specific attributions of increased risk to the use of nuclear power. Public suspicion of nuclear power has been central to the stagnation of this source of fuel in the US, which it suffices to comment, has been bad from a public health perspective, and probably from an environmental perspective, too (depending on semi-philosophical valuations pertaining to long-term management of nuclear waste). Disease outbreaks attributable to the anti-vaccination movement are an even more tangible illustration of the power that misplaced distrust in technological interventions can have on the public.

The vaccination and nuclear power sagas show that vocal minorities of skeptics can have large externalities. Research on the cultural associations of cancer has shown the high potential for an emotional, techno-skeptic response to a perceived increase in threat, and research on risk perception has shown that cancer is particularly likely to draw attention. Meanwhile, the media seem to benefit from a lack of consensus on their responsibilities in risk communication to generate interest in their content -- interest that would vanish if the public knew the underlying facts.

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