Breast Cancer Can Regress Without Treatment, Says Study

Some breast cancers picked up by routine screening and treated with surgery and chemotherapy would have regressed naturally if they had been left, scientists said last night. Research published in a leading medical journal will reopen the debate over breast screening.

The paper, in the Archives of Internal Medicine, says screening programs pick up cancers that are not a threat to health, leading to invasive and unnecessary treatment. But in the current state of technology, it is impossible to know which cancers would have regressed if left, and which would have gone on to kill. The incidence of breast cancer has risen in every European country with screening.

Per-Henrik Zahl and colleagues from the Norwegian Institute of Public Health in Oslo studied a national screening program introduced in the country. "If all of these newly-detected cancers were destined to progress and become clinically evident as women age, a fall in incidence among older women should soon follow," the authors write. "The fact that this decrease is not evident raises the question: what is the natural history of these additional screen-detected cancers?"

They compared breast cancer rates among nearly 120,000 women aged 50 to 64 who were called for three rounds of mammograms between 1996 and 2001 with the rates among women between 50 and 64 in 1992, before the program began. The researchers found that invasive breast cancer was 22% higher in the screened group than in the unscreened group, regardless of age. The researchers say there have been 32 documented cases of breast cancer regression. While that is a relatively small number in a common disease, it does not follow that regression is rare. "It may instead reflect the fact that these cancers are rarely allowed to follow their natural course," they write.

In an editorial, Robert M Kaplan of the University of California, Los Angeles, and Franz Porzsolt of University hospital, Ulm, Germany, say: "Despite the appeal of early detection of breast cancer, uncertainty about the value of mammography continues." Little is known about what happens to women with untreated breast cancer, they say, even though a significant number of women die without knowing they have the disease.

Dr Alexis Willet from Breakthrough Breast Cancer said it was an interesting theory, "however it is not currently possible to predict whether early changes picked up by screening will progress." NHS breast screening program saved lives by detecting cancer early.