Hard on the heels of successful trials of a cervical cancer vaccine came a cause for optimism this week about another form of tumour.

A study by Cancer Research UK (Cruk) has revealed remarkable improvements in breast cancer prognosis: 64 per cent of patients with early breast tumours can now expect to survive for 20 years, compared with 44 per cent in the early 1990s. This has come even before the impact of new drugs such as Herceptin, which have brought further benefits elsewhere, are taken into account. Research in this field is notorious for its setbacks and false dawns, and no one would profess that breast cancer, indeed any cancer, is yet a properly understood disease. But the progress being made is real.

That, however, is not the impression given by another recent report. The UK Working Group on Primary Prevention of Breast Cancer claims instead that doctors, scientists, industry and politicans have wilfully misunderstood the disease at a cost of thousands of lives.

Breast Cancer — an Environmental Disease purports to uncover “incontrovertible evidence” that exposure to man-made chemicals is a huge and preventable cause of breast tumours. This is — of course — being ignored by the “cancer establishment”. “Women have been sold the myth that breast cancer is normal and inevitable. It’s not, ” says Diana Ward, the lead author. “Our bodies have become long-term storage centres for synthetic chemicals and the implications for hormone-dependent diseases like breast cancer are huge.”

It is true that the incidence of breast cancer is rising in Britain, as in other developed countries. Though the reasons are not clear, many factors are now well attested. Alcohol and obesity play a part, as does the rising average age of motherhood and the increasing number of childless women: pregnancy and breast-feeding have a protective effect.

What there isn’t, however, is incontrovertible evidence that synthetic chemicals are even partially responsible, let alone key. The theory that substances that mimic hormones might have an influence is not biologically implausible, though womenare exposed to far higher levels of natural oestrogens. But there is no data to back it up, and not for want of looking: findings are largely negative.

As Lesley Walker of Cruk says: “There is currently no compelling scientific evidence for the role of pollutants in breast-cancer risk.”

That becomes clear on reading the Working Group report. It is littered with assertions linking breast cancer to pollution, yet barely a handful come from the peer-reviewed journals you would expect to be referenced in a medically significant study. The most heavily cited sources are the Ecologist magazine, the newsletter of the Pesticide Action Network, a Guardian supplement, and a book by John Humphrys. It’s not quite Nature or the Lancet.

The authors have apparently cherry-picked quotes and studies that support their case and left out the much larger body of evidence that does not. The conclusion has come first and then arguments to support it.

Even the Working Group’s self-awarded title conveys a spurious authority. It comprises a tiny charity that few oncologists had previously heard of, a trade union and an environmental pressure group.

The suspicion, at a time when the European Parliament is debating legislation on chemicals, is that the report aims more to influence this process than to contribute to breast cancer research. The leading charities such as Breakthrough Breast Cancer and Cruk have dismissed its findings. They prefer, quite properly, to concentrate on the well-grounded science that has delivered the improvements in survival rates announced this week.

It is almost certainly true that many cases of breast cancer have an environmental component. But shrill campaigning documents masquerading as “research” will do nothing to identify them.

Mark Henderson is the Times science correspondent

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