NEW YORK • Thousands of American women each year are told they have a very early stage of breast cancer - Stage 0, as it is commonly known - a possible precursor to what could be a deadly tumour. And almost every one of the women has had either a lumpectomy or a mastectomy, and often a double mastectomy, removing a healthy breast as well.
Yet it now appears that treatment may make no difference in their outcomes. Patients with this condition had close to the same likelihood of dying from breast cancer as women in the general population, and the few who died did so despite treatment, not for lack of it, researchers reported on Thursday in JAMA Oncology, an online weekly medical journal.
Their conclusions were based on the most extensive collection of data analysed on the condition, abnormal cells confined to the milk ducts of the breast, known as ductal carcinoma in situ, or DCIS: 100,000 women were studied over a period of 20 years.
The findings are likely to fan debate over whether patients are undergoing unnecessary and sometimes-disfiguring treatments for conditions unlikely to develop into life-threatening cancers.
Diagnoses of DCIS have soared in recent decades, and they now account for as much as a quarter of cancer diagnoses made with mammography. But new data has raised provocative questions about whether DCIS is cancer, a precursor to the cancer, or just a risk factor - and whether DCIS patients should receive brutal therapies.
Dr Otis Brawley, chief medical officer at the American Cancer Society, said he was not ready to abandon treatment until a large clinical trial is done that randomly assigns women to receive mastectomies, lumpectomies or no treatment for DCIS, and that shows treatment is unnecessary for most patients.
He has no doubt that treatment had been excessive.
Of the 100,000 patients examined, the study found that their chance of dying from breast cancer in the two decades after treatment was 3.3 per cent, no matter which procedure they had, about the same as an average woman's chance of dying from breast cancer, said Dr Laura Esserman, a breast cancer surgeon and researcher at the University of California in San Francisco.
Dr Esserman said that if deadly breast cancers started out as DCIS, the incidence of invasive breast cancers should have plummeted with rising detection rates, which has not happened.
Dr Brawley said the new study, by showing which DCIS patients were at highest risk, would help enormously in defining who might benefit from treatment.
He added that he would like to see clinical trials to check whether the others with DCIS (80 per cent) would be fine without treatment or with anti-oestrogen drugs such as tamoxifen or raloxifene that can reduce overall breast cancer risk.
NEW YORK TIMES