SAN ANTONIO—Accelerated partial breast irradiation (APBI) using intensity-modulation radiotherapy (IMRT) does not appear to reduce local tumor recurrence or overall survival (OS) when compared with external whole-breast irradiation (WBI), according to findings from a randomized equivalence study of 520 women with early-stage breast cancer presented at the 2014 San Antonio Breast Cancer Symposium.

“No statistical difference in terms of ipsilateral breast tumor recurrences [IBTR] was shown between the two arms,” reported lead study author Lorenzo Livi, MD, of the Radiotherapy-Oncology Unit, Florence University Hospital in Florence, Italy. APBI had a better toxicity profile, he also noted.

Study participants were women older than age 40 with early-stage breast cancer, with maximum tumor diameters of 25 mm, and who were deemed suitable for breast-conserving surgery. Enrolled between 2005 and 2013, 520 study participants were randomly assigned at a 1:1 ratio to receive either WBI (260 patients; 50 Gy in 25 fractions followed by 10 Gy boost in 5 fractions) or APBI using IMRT (260 patients; 30 Gy in 5 fractions to tumor bed).

“The prespecified equivalence margin was local recurrence of 5% in the APBI arm,” Dr. Livi reported.  Treatment tolerance was assessed using the acute and late radiation morbidity scoring scheme from Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC).

At a median follow-up of 5 years, the IBTR rate was 1.5%  among women in the APBI group, compared with 1.4% in the WBI group, which was a statistically insignificant difference (P=0.86), Dr. Livi said. Mean time to IBTR was 2.9 years (range 1-4).

The 5-year OS was 96.6% for the WBI group and 99.4% for APBI group, which was also not a statistically significant difference (P=0.057), Dr. Livi said. Five-year rates for distant metastases and IBTR were also statistically similar (P>0.85, not significant).

In both treatment groups the cosmetic result was rated as excellent for more than 90% of patients.

“No grade 3 toxicity was observed for APBI or WBI,” Dr. Livi reported. “Early late side effects included only two cases (0.8%) of grade 2 skin fibrosis in the WBI group.” Overall, APBI group showed better outcome compared with the WBI group (P=0.045).”

“To our knowledge this is the first randomized study using IMRT technique for APBI delivery,”

Reference

  1. Livi L, Meattini I, Marrazzo L et al. S5-03. Presented at: San Antonio Breast Cancer Symposium 2014. Dec. 9-13, 2014; San Antonio, TX.