The study found that the women did not get radiation or lymph-node biopsies, both called for by standard treatment guidelines. Such incomplete treatment can double a patient's risk that the cancer will come back.
And, adding to the concern, more and more women are having lumpectomy instead of mastectomy, said Dr. Ann Butler Nattinger, a professor of medicine at the Medical College of Wisconsin in Milwaukee and lead author of the study. It appears Friday in The Lancet, a British medical journal.
Dr. Nattinger's study, based on the records of nearly 145,000 women treated from 1983 to 1995, did not explain why the recommended procedures were sometimes skipped. Dr. Nattinger suggested that some doctors might not know the treatment guidelines, might disagree with them or might disregard them in certain cases.
The current recommendations for treating early-stage breast cancer, issued by the National Institutes of Health in 1990, call for either mastectomy or breast-conserving surgery like lumpectomy. But neither procedure is sufficient by itself.
Both operations are supposed to include lymph node biopsies to see if the cancer has spread and the patient needs chemotherapy. Women who have mastectomy usually do not need radiation, but lumpectomy, even for tiny tumors, should be followed by radiation.
Dr. Nattinger said patients should learn as much as possible about breast cancer, seek second opinions and get their treatment from a team of doctors that includes specialists in radiation and chemotherapy as well as surgeons.
Dr. Nattinger and her colleagues based their conclusions on medical records of 144,759 women 30 and older who were treated for early breast cancer from 1983 to 1995.