Shelley Hwang, MD, MPH

Shelley Hwang, MD, MPH, the Mary and Deryl Hart Distinguished Professor of Surgery, Duke University School of Medicine in North Carolina, discussed the APBI IMRT Florence trial in a meeting highlights session at the San Antonio Breast Cancer Symposium. She called physician-reported cosmesis “the most striking outcome” in the study, noting, “Even though the bars look similar [on a graph], there were more patients in the [accelerated partial-breast irradiation] group whose physicians thought had excellent cosmetic outcomes.”

The study found no difference in ipsilateral or locoregional tumor recurrences at 10 years and no unanticipated acute and late toxicities, she noted.

Putting the study into context, she referenced the similar ­NSABP-B39 study reported in San Antonio in 2018.¹ The ipsilateral tumor recurrence rate at 10 years in that study was 4.6% with accelerated partial-breast irradiation and 3.9% with whole-breast irradiation—a difference of only 0.7%. Based on the study’s statistical plan, this small difference did not meet the criteria for equivalence, “but the 10-year rate of recurrence was very low in both groups,” she said.

A Crowded Field

Dr. Hwang pointed out that partial-breast irradiation in the current study was not compared to the “usual” hypofractionation regimens used in many centers today—in which radiotherapy is given over 3 weeks and not 5 weeks. In the current comparison, the advantage of an even shorter course of partial-breast irradiation “is not nullified,” she maintained, “but it would definitely not be as strong a factor as when compared to the 5- to 6-week regimens.”

“But in the United States, access to [accelerated partial-breast irradiation] is still not universal,” Dr. Hwang continued. “And it’s a crowded field, with many approaches for administering radiation. Also complicating the field are the emerging technologies for small-dose radiotherapy, preoperative radiotherapy, and even omission of radiotherapy in some prospective clinical trials.”

Meanwhile, she concluded, “Based on this study and B-39…, in low-risk patients considered suitable for [accelerated partial-breast irradiation] based on ASCO and [American Society for Radiation Oncology] guidelines, and for whom duration of therapy is a factor, [partial-breast irradiation] is reasonable.”

Patient Selection

C. Kent Osborne, MD, FASCO, Director of the Dan L. Duncan Cancer Center and Professor of Medicine and Molecular and Cellular Biology at Baylor College of Medicine, Houston, said the study will “likely have some impact” and, in fact, “could be practice-changing for the right patient.”

He said he would select patients according to the trial’s eligibility criteria: node-negative, negative margins, and T1 tumors up to 2.5 cm. “For any patient with small tumors and negative surgical margins, I think this is a reasonable approach,” he said. “In fact, when I get back to the clinic, I’ll talk to my radiation oncologists about these findings.”

Dr. Osborne also said accelerated partial-breast irradiation will be welcomed by patients who must travel some distance for treatment. “A shorter course of radiation would certainly improve quality of life,” he commented. 

DISCLOSURE: Dr. Hwang reported no conflicts of interest. Dr. Osborne has served on advisory boards for Genentech and AstraZeneca, served as a consultant for Tolmar Pharma, and holds stock in GeneTex.

REFERENCE

1. Vicini FA, Cecchini RS, White JR, et al: Primary results of NSABP B-39/ RTOG 0413 (NRG Oncology): A randomized phase III study of conventional whole breast irradiation vs partial breast irradiation for women with stage 0, I, or II breast cancer. 2018 San Antonio Breast Cancer Symposium. Abstract GS4-04. Presented December 6, 2018.