For example, patients may abandon healthy lifestyles (exercising, eating plenty of fruit and vegetables, giving up smoking) if they believe that screening will pick up cancers at an early stage.

How Far Should We Compromise on Scientific Proof?

The crucial question is the following: how much evidence (and at what level in the well-known hierarchy of evidence [http:⁄⁄www.shef.ac.uk/ scharr/ir/units/systrev/hierarchy. htm]) is required before implementing national screening programmes? The World Health Organization guidelines for screening request evidence for mortality and morbidity reduction from high-quality randomised controlled trials before starting any population screening programme [25]. In other fields of medicine, such as pharmacotherapy, randomised trials have been a standard requirement for introducing any new drug on the market.

Many health services have admittedly been introduced based on much weaker evidence than we now have for CRC screening. But historic substandards should be no argument for turning a blind eye to the need for the best-quality evidence or for allowing health policy decisions to be based more on ideology and convictions than science. Also, the concept of pushing a screening service onto presumably healthy people is quite different from establishing a health service that people seek when they feel sick. The level of evidence should therefore be more foolproof for screening services than for other services, and the evidence should be able to withstand debates such as the one surrounding mammography. High-quality evidence on CRC screening would also help to unite the somewhat divergent professional views on this intervention.

The Finnish Model

We need to recognise that some countries feel that the introduction of national CRC screening programmes is an urgent matter. Ideally, these should be rolled out in a stepwise, randomised fashion, just as Finland has done (see Box 1), allowing evaluation of its FOBT screening programme after five years before deciding what their next step of action should be [26]. The people behind the Finnish strategy deserve credit for persuading their politicians to choose this cautious, stepwise model, and the politicians and health authorities deserve credit for listening.

In the Finnish model, half of each age cohort is randomised to screening or no screening. The Finnish model must have required a lot of explanation to authorities that this approach was clearly the best way to proceed. It was, of course, risky for politicians to voluntarily throw away half (or more) of their target candidate supporters by declaring, in essence, “We believe in CRC screening, but aren’t sure about it, and half of you will be offered screening while the other half will not”.

In contrast to the Finnish approach, there have been examples of political decisions to simply screen everyone or none at all, i.e., to reject the idea of large-scale randomised trials. This rejection may leave health-care providers and doctors with a very diffi cult choice: either to go straight for national screening or to reject the political offer and wait for a new set of politicians who may understand the need for further randomised trials.

Short-Term Gain, Long-Term Pain?

For those who have experienced CRC or have been close to someone suffering from it (a considerable number in Westernised societies), any proven benefi t from screening will do. Furthermore, CRC screening may appear politically attractive and tempting to politicians when campaigning for a general election. And cost–benefi t estimates have even suggested that such screening may be economically sound and at least as cost-effective as established national screening programmes (for breast and cervical cancer) [27].

But politicians should be concerned about whether CRC screening is the right way to spend available resources and taxpayers’ money for the benefit of individuals, families, employers, and the community. There are still few data to guide decisions about CRC screening. It is hard to understand why politicians are reluctant to invest in randomised clinical trials, since the results of these will equip them to make better political decisions in the end.

The alternative to taking a firm grip on development toward national programmes through the funding of large, well-designed randomised controlled trials seems to be uncontrolled out-of-pocket expenditure on sporadic screening, which cannot generate any real evidence about the effectiveness of screening. Any country considering national CRC screening can surely afford to do its own randomised trials, but time is running out. Could it be that none of the providers really want to know, but prefer to make decisions by convictions and “gut feelings” for short-term gain? For a screening programme to survive over time, it has to deliver according to expectations. If expectations are not based on trials referable to the target population, any programme will be vulnerable to devastating debates, such as those surrounding mammographic screening seen in some countries.

Health policymakers must also remain sceptical of the role of celebrity endorsements. Communication on complex decisions such as cancer screening, with an aim to inform rather than persuade, is not an obvious task for celebrities [28]. Likewise, it is not an obvious task for doctors to take on the role of politicians. Instead, politicians must accept the need for more science in their decision making. We need more objective facts, relevant to the target population, to be communicated—and not personal convictions that doctors, doctorpoliticians, and politicians only present as “facts”. To paraphrase former US President Franklin Delano Roosevelt: “Look to Finland”.

Citation: Hoff G, Bretthauer M (2006) The science and politics of colorectal cancer. PLoS Med 3(1): e36.

Copyright: © 2006 Hoff and Bretthauer. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abbreviations: CRC, colorectal cancer; FOBT, faecal occult blood test Geir Hoff and Michael Bretthauer are at the Institute of Population-Based Cancer Research, Oslo, Norway.

Geir Hoff is also at the Telemark Hospital, Skien, Norway. Michael Bretthauer is also at the Department of Medicine, Rikshospitalet University Hospital, Oslo, Norway.

* To whom correspondence should be addressed. E-mail: hofg@kreftregisteret.no

Competing Interests: The authors declare that they have no competing interests.

DOI: 10.1371/journal.pmed.0030036