TORONTO – Breast-cancer screening has long been viewed as one of the most important tools for reducing mortality from the disease. That is why recent doubts about its effectiveness – intensified by the publication in February of the 25-year follow-up to the Canadian National Breast Screening Study – have come as such a shock. How can breast-cancer screening, which facilitates early detection of the disease, not prevent deaths from it?
Understanding screening’s limitations requires, first and foremost, an understanding of the process. A mammogram (x-ray of the breast) is administered to ostensibly healthy people to detect unsuspected disease. If any abnormalities are found, a diagnostic test is conducted to confirm the presence of the disease. If the results are positive, treatment begins.
The first limitation of breast-cancer screening is obvious: where effective diagnosis and treatment are not available, screening cannot have any impact. But there is more to the issue – namely, whether screening ultimately fulfills its intended purpose of reducing breast-cancer mortality rates.
There have been several attempts to evaluate, through observational studies, the impact of screening in the general population. But such studies, which are based on comparisons between uncontrolled groups, tend to produce biased results. None has been able to account for differences in treatment. More important, none has found a reduction in advanced breast cancer in the screened groups – a requirement to deem screening effective.
With observational studies producing inadequate results, scientists turned to a procedure developed years ago to evaluate new tuberculosis drugs: randomized screening trials. Such trials begin with the selection of women at risk of developing breast cancer, and randomly allocate them to be screened or not.
Any woman in either group who develops breast cancer is treated to the fullest extent possible, following the closest possible treatment plan to other participants in the trial (taking into consideration the stage of the disease at diagnosis). Researchers follow the women’s progress over many years, with the goal of comparing the two groups’ mortality rates.
In North America, where, for ethical reasons, randomization requires informed consent, only two such trials have been conducted. The first was in New York in the 1960s, using annual mammograms and breast examinations for the screened group.
The second, the Canadian National Breast Screening Study, which began in the 1980s, also used annual mammograms and breast examinations for the screened group. But, in the control group, women aged 50-59 also received annual clinical breast examinations, and women aged 40-49 were given a single breast examination.
In Europe, one trial began in the United Kingdom in the 1970s, again using breast examinations and mammography for the screened group. A more recent British trial, performed on women aged 39-41, used only mammography, as did the largest of all, the Swedish two-county trial. Though the trial results have been inconsistent, the conclusion is clear: breast-cancer screening does not reduce mortality rates.
The trials that have shown a significant decrease in mortality are usually older, and other factors have compromised the results. For example, the Swedish two-county trial was randomized by clusters of population groups, and the comparability between the women in the screened and control groups was not confirmed. Moreover, the trial was conducted before modern breast-cancer treatments were freely available.
More recent trials, such as that conducted in the UK, show at most a non-significant benefit from screening. The results of the 25-year follow-up of the Canadian trial – which can be considered the most accurate, given that the women were carefully characterized according to risk factors and had access to the most advanced treatments – are even more damning.
Beyond showing no benefit from mammography screening, the Canadian trial highlighted one of the practice’s major disadvantages: over-diagnosis. Indeed, 22% of those in the screened group were over-diagnosed, meaning that the cancers found would not have become clinically detectable during the woman’s lifetime. Add to that the in situ cancers – early-stage cancers that have not spread to neighboring tissue – and the number rises to 50%.
To be sure, over-diagnosis is inevitable with good screening tests. The real problem is the over-treatment that follows, owing to the lack of reliable tests to differentiate observable lesions from those that actually require medical intervention.
Many of the women who believe that their lives were saved by mammography screenings actually had so-called “IDLE” cancers (indolent lesions of epithelial origin), which would not have progressed before they died of other causes. Meanwhile, the very aggressive cancers, which are most likely to prove fatal, tend to present as “interval” cancers that appear between screenings. In the deadliest cases, regular screenings would not make much difference.
Efforts to develop new, more sensitive screening tests are thus likely to do more harm than good, as they increase the rate of over-diagnosis, without improving outcomes among women with aggressive cancers. What breast-cancer patients really need are tests that identify the risk that the disease actually poses, as well as new, lifesaving treatments. It is time to recognize that breast-cancer screening does not save lives – and to focus on the strategies that will.
Anthony B. Miller is Professor Emeritus at the Dalla Lana School of Public Health, University of Toronto.
Getting Investment in Europe Right
By Jean Pisani-Ferry
PARIS – The European Commission’s new president, Jean-Claude Juncker, has put public investment back on the agenda with his idea of a three-year €300 billion ($378 billion) capital spending plan. The European Union’s leaders are expected to discuss his proposal in December. Everyone seems to agree that more investment would help to strengthen a worryingly feeble European economy. But, behind the superficial consensus, many questions remain unanswered.
For starters, this is not the first time that Europe has considered such an initiative. In 1993, the Commission, under Jacques Delors, proposed a capital spending plan in its White Paper on growth, competitiveness and employment. The plan was broadly endorsed, but no action was taken. Likewise, in 2000, as part of its Lisbon Strategy, the EU sought to increase national spending on research and development to 3% of GDP. It failed to reach this target. More recently, in June 2012, EU leaders adopted a Compact for Growth and Jobs that was supposed to mobilize €120 billion. The check is still in the mail.
It is indeed easy to pretend to act without taking effective action. One way is to ask the European Investment Bank (EIB), the EU’s development bank, to lend more. Such calls face two limitations: the EIB itself is careful not to jeopardize its financial rating by taking on too much risk, and its loans easily substitute for private financing. More lending therefore can be pointless if it results in the EIB crowding out private financing of the best available projects. A bridge financed by the EIB may be more affordable than one financed by capital markets, but it remains the same bridge and has the same economic impact. The size of the EIB’s balance sheet is not a good measure of its effectiveness.
Instead, three investment levers should be used. The first lever is budgetary: Governments that enjoy fiscal space should spend on economically sound projects. Public investment is a complement to private investment; if designed and targeted well, it can trigger more private investment, rather than crowding it out.
For example, adequate transport and broadband infrastructure favors the burgeoning of business initiatives. At a time when markets are willing to lend to solvent governments at historically low rates, there should be little room for hesitation.
Obviously, cheap financing does not justify public investment in projects with dubious social returns, or what development practitioners call “white elephants”: headline-grabbing projects of disputable value but supported by special interests. Investments should be assessed on the basis of their overall economic impact, with proper procedures put in place to prevent public money from being wasted.
The second lever for investment is regulatory in nature. Many large-scale investments that only pay off over the long term – for example, in energy, digital infrastructure, and transport – are concentrated in state-regulated sectors, giving governments the power to influence business decisions.
Predictability regarding the future course of regulation would unlock projects held back by uncertainty. A credible outlook for the price of carbon, for example, would prompt new private-sector investment in cleaner technologies. Similarly, an agreed European framework for projects that connect countries would remove obstacles to cross-border investment.
These conditions are a long way from being met, which means that profitable investments are not being made. Changing that would not cost a single euro; it requires only political resolve.
The third lever is financial. Investment demand has slackened not because interest rates are too high, but because there is not enough risk appetite within the banking system. Financing in continental Europe is traditionally bank-based, unlike in the US, where capital markets reign supreme. But banks are being told by regulators to reduce their leverage and to post higher capital when they embark on risky lending, and their creditors are being told that they should not expect to be bailed out if banks get into trouble.
This is intentional. Governments and citizens in Europe have paid – and are still paying – an astronomically high price for the reckless lending and investment of the 2000s. Understandably, they do not want to repeat the experience.
The consequence, however, is that high-risk, high-return projects are more difficult to finance than they should be. If Europe wants to revive its economy and escape stagnation, it needs entrepreneurs to take more risk to innovate. But its financial system is undergoing a transition from a bank-based to a market-based system that involves risk aversion.
This is where the public side – both national governments and the EU – should step in and share some of the risk with private players. They should temporarily behave more like investors who scrutinize projects, contribute funding, and earn returns. Using the EIB and national development banks to this end would help overcome the current impasse. Would these three types of initiatives add up to €300 billion? No one knows at this stage. But this route would be the surest way to reach the goal.
Jean Pisani-Ferry is a professor at the Hertie School of Governance in Berlin, and currently serves as the French government’s Commissioner-General for Policy Planning. He is a former director of Bruegel, the Brussels-based economic think tank.
Copyright: Project Syndicate, 2014.