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Comparing Breast Irradiation Regimens in Preventing Local Recurrence

By: Celeste L. Dixon
Posted: Tuesday, February 5, 2019

Accelerated partial-breast irradiation (APBI) using three-dimensional conformal radiotherapy (3D-CRT), an alternative to whole-breast irradiation (WBI), was found to be noninferior after surgery in terms of 5-year ipsilateral breast tumor recurrence, according to study results presented at 2018 San Antonio Breast Cancer Symposium (Abstract GS4-03). Although the less aggressive regimen was linked to less acute toxicity, more late normal tissue toxicity and adverse cosmesis were reported with APBI.

The RAPID trial evaluated APBI delivered with 3D-CRT, which, in its ability to shape radiation beams to match tumor shape, allows more precise radiation targeting and more sparing of normal tissue. In addition, APBI allows radiation treatments to be completed in up to 1 week, versus 3 to 6 weeks with WBI. The investigators were led by Timothy J. Whelan, BSc, BM, BCh, MSc, of McMaster University, Hamilton, Ontario, Canada.

Eligible women were aged ≥ 40 years with either axillary node–negative invasive ductal carcinoma or ductal carcinoma in situ ≤ 3 cm treated by breast-conserving surgery with clear margins. Between 2006 and 2011, 2,135 patients (median age, 61 years) from Canada, Australia, and New Zealand were randomly assigned equally to undergo WBI or APBI using 3D-CRT.

The 5-year and 8-year cumulative rates of ipsilateral breast tumor recurrence with APBI were 2.3% and 3.0%, respectively, whereas with WBI , the corresponding rates were 1.7% and 2.8%. The hazard ratio for APBI versus WBI was 1.27. The median follow-up was 8.6 years.

APBI “was associated with less acute toxicity,” but it also was associated with “an increase in late normal tissue toxicity,” the authors reported. In addition, the rate of adverse cosmesis was significantly higher with APBI than with WBI at 3 years (29% vs. 17%) and 5 years (32% vs. 16%).

Disclosure: Study authors’ disclosures can be found at SABCS.org.



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