The less aggressive of the two breast-conserving surgeries risked the need for a further operation.
The "excision of a cavity shave margin" - which means removing more tissue during a lumpectomy surgery in the treatment of breast cancer - was also found to reduce the likelihood of cancer cells being found at the edge of the removed lump.
The results of the randomized trial to compare half the surgeons doing greater excision versus half the surgeons doing a normal partial mastectomy without the deeper cutting are published in The New England Journal of Medicine.
They were also presented at the 2015 annual meeting of the American Society of Clinical Oncology in Chicago, IL.
Whether a woman would have cavity shave margins resected - removing further tissue from the surface of the cavity left by the excised tumor - was decided randomly during the operations.
Having the intervention significantly lowered the rate of positive margins - cancer cells found at the edge of removed lumps:
- The "shave" group produced positive margins at a rate of 19% - and also saw a lower rate, at 10%, of second surgeries being needed to go back for margin clearance
- Whereas the "no-shave" group showed 34% positive margins - and a 21% rate of second operations.
The study also measured other outcomes, as explained by lead author Dr. Anees Chagpar, associate professor of cancer surgery at the Yale School of Medicine in New Haven, CT:
"Taking cavity shave margins cut the positive margin rate in half, without compromising cosmetic outcome or increasing complication rates."
Also director of the breast center at the Smilow Cancer Hospital at Yale-New Haven, Dr. Chagpar says: "Despite their best efforts, surgeons could not predict where the cancer was close to the edge."
Trial has the potential to have 'huge impact' for patients
Dr. Chagpar adds: "This randomized controlled trial has the potential to have a huge impact for breast cancer patients.
"No one likes going back to the operating room, especially not the patients who face the emotional burden of another surgery."
The most recent statistics held by the US Centers for Disease Control and Prevention show that in 2011, some 220,097 women in the US were diagnosed with breast cancer.
Dr. Chagpar says that between 20% and 40% of those who undergo breast-conserving surgery with a partial mastectomy to remove the disease have positive margins.
The randomized trial involved 235 patients enrolled at the Smilow Cancer Hospital with breast cancer ranging from stage 0 to stage III. They will be followed for 5 years to evaluate the impact of the technique on recurrence rates.
The authors say in the publication:
"We found that the perception of the cosmetic outcome was equivalent in the two groups among patients who were unaware of their study-group assignment, despite the fact that the shave group had more tissue excised."