And Dr. Susan Love of the Dr. Susan Love Research Foundation, said: "I do think these findings are practice-changing."
Love cautioned that the TARGIT approach needs specialized equipment that is not widely available, "which may limit its adoption" and she also noted the short follow-up.
But, she said, "for too long studies have just added more and more invasive surgery, radiation and chemotherapy. It is about time that we explored how we can also do less." Her foundation, based in Santa Monica, Calif., finances research into breast cancer.
Some experts worry that the relatively low dose used in the TARGIT approach may not be enough. Typically, external beam radiotherapy -- the current standard of care -- gives 40 to 56 Gray of radiation, often with a boost of another 10 of 15 Gray.
In the TARGIT procedure, the surface of the tumor bed typically receives 20 Gray that attenuates to between five and seven Gray at a depth of one centimeter.
"We think that the dose of radiation used ... is rather low and we are concerned about the long term results," said Dr. Alphonse Taghian of Massachusetts General Hospital in Boston.
Taghian said his institution uses PBI "off protocol for a selected group of patients" but only with the 3-D conformal technique. They "would not use the intraoperative technique as described in the Lancet paper," he said in an email.
On the other hand, "use in selected patients now is rational, especially frail elderly patients with small, excellent-prognosis tumors," according to Dr. Larry Norton of Memorial Sloan-Kettering Cancer Center in New York city.
For most patients, though, it's still experimental, he said in an email, adding he would not suggest using the approach.
"Before we abandon the existing technique with its excellent local control and cosmetic long-term outcomes, we need much more long-term data," Norton said. As well, he said, "intraoperative radiotherapy requires expensive machinery and space and also ties up space that could otherwise be used for surgery."
Dr. Beryl McCormick, also of Memorial Sloan-Kettering, noted that a recent consensus statement from the American Society of Radiation Oncology recommends partial breast radiation only for women 60 or older with favorable early stage disease.
She said a study similar to the TARGIT trial, conducted at Memorial Sloan-Kettering, had good results but needed special equipment, such as an operating room shielded for high dose radiation, which would make it not applicable for most patients in the U.S.
That said, McCormick said she'd only recommend the procedure in the context of a clinical trial.
"The TARGIT trial is hypothesis generating, because of the unusually low dose given, but I wouldn't call it 'practice changing'," she said in an email.