Background
Updated ASTRO evidence-based consensus statement on accelerated partial breast irradiation (APBI) for early-stage breast cancer after BCS. This 2017 update revised and replaced the 2009 ASTRO consensus statement, incorporating data from interim analyses of multiple APBI RCTs (RAPID, IMPORT LOW, NSABP B-39/RTOG 0413) and retrospective series. Classifies patients into Suitable, Cautionary, and Unsuitable categories for APBI outside of a clinical trial.
Interventions and follow up
Arm A: N/A — consensus statement, not an RCT
Arm B: N/A
Primary endpoint: Classification framework for APBI patient selectio
mFollow up: N/A (based on reviewed literature)
Arm B: N/A
Primary endpoint: Classification framework for APBI patient selectio
mFollow up: N/A (based on reviewed literature)
Results
Suitable for APBI: Age ≥50, BRCA1/2 negative or unknown, T1 (≤2 cm), pN0, ER+, no LVI, margins ≥2 mm, unifocal, ductal histology or favorable special types, no EIC, pure DCIS ≥50 and ≤3 cm with favorable features
Cautionary: Age 40–49, T2 (2.1–3 cm), or limited LVI, or ER−, or close margins (1–2 mm), or pure DCIS with other features
Unsuitable: T3+, pN1-3, multicentric, positive margins, extensive LVI, prior RT
Cautionary: Age 40–49, T2 (2.1–3 cm), or limited LVI, or ER−, or close margins (1–2 mm), or pure DCIS with other features
Unsuitable: T3+, pN1-3, multicentric, positive margins, extensive LVI, prior RT
Adverse events
Main adverse events: APBI modalities (brachytherapy, 3D-CRT, IORT) have modality-specific toxicity profiles. Brachytherapy is associated with fat necrosis and infection; 3D-CRT with fibrosis and cosmetic changes; IORT with poor cosmesis in some patients. RAPID trial showed higher rates of adverse cosmesis with 3D-CRT APBI at 3 years.
Conclusions
APBI is an acceptable alternative to whole breast irradiation in appropriately selected patients. Suitable patients are those with small, node-negative, ER+, unifocal invasive tumors with adequate margins and age ≥50. For Cautionary patients, enrollment in a clinical trial is preferred. For Unsuitable patients, APBI is not recommended outside of a trial.
Key Limitations
Key Limitations: Consensus statement based on retrospective data and interim trial results — randomized data at the time of publication were immature. NSABP B-39 showed non-inferiority was not met (higher ipsilateral breast tumor recurrence with APBI), subsequently downgrading enthusiasm for APBI in some categories. 2022 ASTRO guideline further refined criteria. Different APBI modalities are not equivalent and may produce different outcomes. Limited data on long-term cosmesis and toxicity for newer APBI techniques.
Clinical Context
APBI offers the practical advantage of a 1–2 week treatment course vs 3–7 weeks for WBI, improving convenience and access. NSABP B-39 (published 2023) showed APBI was non-inferior in 10-year IBTR in suitable patients using 3D-CRT or brachytherapy, supporting APBI use in appropriately selected patients. IORT (TARGIT-A, ELIOT) showed higher local recurrence rates than WBI in selected settings. Brachytherapy APBI (MammoSite, SAVI) has higher local toxicity than external-beam APBI.
References