medwireNews: Long-term ipsilateral breast tumor recurrence (IBTR) rates are similar whether women are treated with accelerated partial-breast irradiation (APBI) or whole-breast irradiation (WBI), results of the phase 3 APBI-IMRT-Florence trial show.
The analysis, among 520 patients with early-stage breast cancer suitable for breast-conserving surgery, also found that APBI was associated with significantly less toxicity and improved cosmetic outcomes relative to WBI.
During a median 10.7 years of follow-up, Icro Meattini (University of Florence, Italy) and co-investigators found that the 10-year cumulative incidence of IBTR was 3.7% among the 260 patients randomly assigned to receive APBI at a dose of 30 Gy in five nonconsecutive daily fractions after breast-conserving surgery.
This was not significantly different from the 10-year cumulative IBTR rate of 2.5% observed among the 260 patients assigned to receive WBI at 50 Gy in 25 fractions with a tumor bed boost following surgery.
There was also no significant difference between the APBI and WBI arms in the 10-year rates of overall survival (91.9% in both), breast cancer–specific survival (97.8 vs 96.7%), locoregional recurrence (3.7 vs 2.9%), and distant metastases (2.9 vs 3.2%).
However, individuals in the APBI arm experienced significantly less acute and late toxicity than those in the WBI arm.
For example, just 2.0% of patients treated with APBI experienced a grade 2 or worse adverse event during the first 6 months after radiotherapy compared with 37.7% of those treated with WBI. Beyond 6 months, there were no grade 2 or worse adverse events reported in the APBI group compared with seven (2.7%) in the WBI group.
And Meattini et al suggest that “[t]hese outcomes might have consequently influenced the cosmesis results,” which were significantly better with APBI than with WBI when judged by both physician and patient.
According to the physicians, 94.7% and 72.7% of patients in the APBI and WBI groups, respectively, had excellent cosmetic outcomes, while 0.0% and 1.9%, respectively, had fair outcomes.
For the patients, the cosmetic outcome was considered excellent in 17.9% of APBI cases and 5.1% of WBI cases, and was fair in 0.8% and 14.6% of cases, respectively.
However, the researchers point out that the WBI treatment schedule “could be considered out of date by today’s standards.”
They say: “Currently, most patients having the characteristics of our series would be treated with moderate hypofractionation WBI without boost, which may result in a better cosmetic outcome compared with conventionally fractionated WBI.”
The authors conclude in the Journal of Clinical Oncology that their “findings add valuable knowledge regarding the choice of the best radiation technique and schedule to prevent adverse toxicity/cosmesis.”
They add that their APBI schedule “should be considered an attractive option when an external APBI approach is chosen to treat a patient with low-risk early [breast cancer].”
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