SAN ANTONIO — A new study adds to the growing evidence that accelerated partial breast irradiation (APBI) after breast conserving surgery provides disease control comparable to that seen with whole breast irradiation (WBI), with better cosmetic results and a shorter, more convenient dosing regimen.
The twist in this study is the use of intensity modulated radiotherapy (IMRT) rather than conventional 3-D conformal radiation or brachytherapy.
Results of a randomized phase 3 trial, reported here at San Antonio Breast Cancer Symposium (SABCS) 2014, show that after 5-year median follow-up, there were no significant differences in either same breast tumor recurrence, distant metastases, or overall survival between women treated with WBI with IMRT delivered over 6 weeks and APBI with IMRT delivered over 2 weeks.
"Accelerated partial breast irradiation obtained better results in terms of acute and late and cosmetic outcomes," said investigator Lorenzo Livi, MD, professor of radiation oncology at Florence University, Italy.
Alphonse Taghian, MD, chief of breast radiation oncology and codirector of the breast cancer research program at Massachusetts General Hospital Cancer Center, in Boston, who was not involved in the study, told Medscape Medical News that the study was well designed and that he was happy to see that outcomes were comparable between APBI and WBI.
He pointed out, however, that although IMRT costs the same as 3-D conformal radiotherapy in Europe, it costs twice as much in the United States, and it is a difficult sell to insurers looking to rein in costs.
"We have been treating patients with APBI since 2003, and we don't use IMRT; we use a different technique which is much cheaper than the 6-week regimens, but also has less exposure of the nontarget breast tissue than IMRT," he said.
"IMRT is a very high attack which will increase exposure of a large volume of tissue which doesn't need to be exposed, but with very small doses of radiation. We can do as well, or probably better, with a technique that is conformal to just the target," he added.
Dr Taghian also noted that in Dr Livi's study, APBI was delivered over 2 weeks, rather than twice daily for one week, as is done in Mass General and some other US centers.
His remarks were echoed in the question-and-response following Dr Livi's presentation.
"I would actually see this as a negative trial from the data we've seen so far," commented Lorie L. Hughes, MD, from Atlanta, Georgia.
"As a radiation oncologist who's trying to think how to reduce the cost of treatment, since we know that IMRT is about three times as expensive as standard 3-D whole breast irradiation, I think this says that with what we have so far, the IMRT technique does not hold an advantage, except for skin toxicity, which I would argue is fairly minimal to begin with. So I think your conclusion is a little sweeping or a little misleading from what you presented here today," she said.
Dr Livi replied that they had good results with the technique, but longer follow-up is needed before they can recommend changing practice. He also noted that in Italy, IMRT is comparable to 3-D conformal radiotherapy in cost, as noted by Dr Taghian.
Is It Safe?
A retrospective study published by investigators at the University of Texas MD Anderson Cancer Center in 2012 compared APBI with brachytherapy to WBI following lumpectomy among women aged 67 years and older. They found that at 5 years, APBI with brachytherapy was associated with a twofold increase in the likelihood of mastectomy and increased postoperative and radiation-related complications, but no difference in overall survival.
But 10-year follow-up from a randomized trial in Hungary, presented at the European Society for Radiotherapy and Oncology 2012 Annual Conference (ESTRO 31), showed similar 10-year local recurrence rates for WBI and APBI delivered by either brachytherapy or electron beam (5.1% vs 5.9%) and similar 10-year cancer-specific survival rates (94% vs 92%).
In the current study, Dr Livi and colleagues enrolled 520 women with early breast cancer treated with breast conserving surgery and randomly assigned them to receive either APBI to the index quadrant, with 30 Gy delivered in 5 fractions of 6 Gy each over 2 weeks, or standard WBI with 50 Gy plus a 10-Gy boost to the tumor bed delivered in 30 fractions of 2 Gy each over 6 weeks.
After a median follow-up of 5 years (range, 0.6 – 9.0 years), in the intention-to-treat analysis, there were no statistically significant differences in either the ipsilateral breast tumor recurrence rate, the 5-year distant metastases rate, or the 5-year overall survival rate.
There were a total of six ipsilateral tumor recurrences, three local relapses occurring in WBI-treated patients and three new tumors occurring in the ipsilateral breast in APBI-treated patients.
There were four locoregional recurrences in the WBI group, and three in the APBI group. There were 10 contralateral tumors, occurring in seven and three patients, respectively. Four patients in the WBI group had distant metastases as either a first or secondary event, as did three patients in the APBI group.
There were eight deaths during follow-up, seven in the WBI group and one in the APBI group. Breast cancer was the cause of death in three and one patients, respectively, with the remainder of deaths attributed to other causes.
The cumulative 5-year incidence rates of ipsilateral tumor recurrence were 1.4% and 1.5%. Skin toxicities were significantly lower among patients treated with APBI (P = .0001), and there were no grade 3 toxicities of any kind in either group.
In all, 337 patients were available for cosmesis evaluation, with a minimum of 48 months' follow-up. More than 90% of patients in each group rated their cosmetic results as "excellent" or "good."
The study was institutionally supported. Dr Livi, Dr Taghian, and Dr Hughes have reported no relevant financial relationships.
San Antonio Breast Cancer Symposium (SABCS) 2014. Abstract S5-03, presented December 12, 2014.
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Cite this: Acclerated IMRT Comparable to WBI at 5 Years - Medscape - Dec 16, 2014.