In a dramatic shift since the publication of margin guidelines for breast cancer surgery, lumpectomy rates have substantially increased and more–aggressive surgical options have been used less often, according to research findings from a new study presented at the 2017 annual meeting of the American Society of Clinical Oncology in Chicago.

The study was published in athe journal JAMA Oncology.

Surgery after an initial lumpectomy to obtain more widely clear margins is common and can often lead to more–aggressive surgery, like mastectomy, in patients who may not need additional treatment.

In a new study, researchers found that since the 2014 publication of margin guidelines that endorsed a minimal negative margin rates of additional surgery after an initial lumpectomy have decreased, leading to an increase in the overall lumpectomy rate and a decrease in the mastectomy rate.

The study found the rate of lumpectomy as the definitive surgical procedure rose by 13 percent, accompanied by a decrease in unilateral (to 18 percent from 27 percent) and bilateral (to 16 percent from 21 percent) mastectomies. Surgery after a lumpectomy, both re–excision and mastectomy, declined by 16 percent overall. The study illustrates that guidelines can be an effective, low–cost approach to addressing clinical controversies.

“The shift away from more–aggressive treatment and the adoption of these guidelines is a positive step in the effort to help women choose the best breast surgery options for them,” says Monica Morrow, MD, chief of the breast surgery service at Memorial Sloan Kettering Cancer Center. Morrow presented the results at ASCO.

“We want women to be confident in their cancer surgery and avoid a mastectomy or additional surgery when medically appropriate. This rapid change, observed within two years of the guidelines’ dissemination, illustrates the willingness of the surgical community to adopt evidence–based practices that improve outcomes for their patients,” she adds.

The rise in mastectomy as a treatment option when not medically necessary has pushed more doctors to research patient decision–making and the role that anxiety plays in their choices. Many women worry about cancer recurrence, and previous research has found that this appears to drive the decision to have a double mastectomy, even though there is no evidence that the procedure improves outcomes. This study demonstrates that the need for a second surgery is a major driver in the decision for some women to undergo a mastectomy and is a benchmark in the efforts to understand ways to safely minimize the use of aggressive surgery.

“Our goal in issuing these guidelines was to save patients from unnecessary surgery while still minimizing the risk of the cancer returning,” says Morrow. “It is heartening to see that this primary aim has been met. With more time and further adoption of these guidelines, we anticipate seeing a greater decline in the use of additional surgery after a lumpectomy.”

“The results of our study underscore a sea change in clinician culture, increasingly committed to harnessing precision medicine to reduce the burden of cancer treatment,” says co–senior author Steven J. Katz, MD, MPH, professor of medicine and of health management and policy at the University of Michigan.