Patients with early-stage breast cancer who underwent adjuvant accelerated partial breast irradiation with multicatheter brachytherapy demonstrated outcomes comparable to those who received standard whole-breast irradiation, according to results of a multicenter, randomized phase 3 trial presented at the ASTRO Annual Meeting.
This is the first phase 3 study to prove noninferiority of accelerated partial breast irradiation (APBI) compared with whole-breast irradiation for selected patients with early-stage breast cancer.
Patients with breast cancer typically receive radiation therapy after breast-conserving surgery to reduce the chance for recurrence or metastasis. Whole-breast irradiation — during which radiation is delivered to the entire breast and often the surrounding chest area for several weeks, followed by a radiation boost to the area from which the cancer was removed — is the standard approach.
Some women who are eligible for breast-conserving surgery opt instead to undergo mastectomy in hopes they can avoid whole-breast irradiation, either due to the duration of the treatment or the risk for radiation-related side effects, according to study background.
Vratislav Strnad, MD, PhD, professor in the department of radiation oncology at University Hospital Erlangen in Germany, and colleagues conducted a randomized noninferiority trial to compare two adjuvant regimens — standard 50 Gy whole-breast irradiation with a tumor bed boost of 10 Gy, or APBI with multicatheter brachytherapy — for women with early-stage breast cancer who underwent breast-conserving surgery.
The APBI technique delivers radiation directly to the tissue at risk, which reduces the risks for adverse effects — particularly to surrounding tissues of the lungs, heart and skin — and also reduces the administration period.
The analysis included 1,184 patients with stage 0, I or IIA breast cancer treated at 16 centers in Europe between April 2004 and July 2009.
All patients were aged 40 years or older, and baseline factors were comparable between treatment groups.
Local recurrence served as the primary endpoint. Secondary endpoints included OS, DFS, cumulative incidence of regional recurrence and distant metastasis, incidence and severity of acute and late side effects, and cosmesis.
Median follow-up was 6.6 years.
Results of the as-treated analysis showed no statistically significant difference between the APBI group and whole-breast irradiation group with regard to 5-year local recurrence (1.4% vs. 0.9%), 5-year DFS (95% vs. 94.5%) and 5-year OS (97.3% vs. 95.6%). The lack of difference in local recurrence rates persisted regardless of patient age, tumor type and additional therapy received (eg, chemotherapy or antihormonal therapy).
Researchers also reported similar rates of second primary ipsilateral breast cancers (1.1% for whole-breast irradiation vs. 0.9% for APBI; difference, -0.2%; 95% CI, -9.15 to 8.75).
Recently published long-term results of several smaller phase 2 trials showed low recurrence rates associated with APBI compared with whole-breast irradiation after breast-conserving treatment.
Consequently, the results of the current study were “not totally surprising,” Strnad said in a press release.
“What is surprising, however, is how clear the results are,” Strnad said. “Our favorable results are in contrast with the disappointing and controversial results reported from other studies that used other APBI techniques, such as intraoperative and external beam radiation therapy.” – by Mark Leiser
Strnad V, et al. Abstract LBA7. Presented at: ASTRO Annual Meeting; Oct. 18-21, 2015; San Antonio.