Accelerated Partial Breast Irradiation for This Patient
Yes, APBI is appropriate for this 55-year-old woman with a 1.8 cm, ER-positive, node-negative, unifocal invasive breast carcinoma with clear surgical margins ≥2 mm after breast-conserving surgery. She meets all the established criteria for APBI as defined by current national guidelines.
Patient Eligibility Assessment
This patient satisfies the NCCN-endorsed ASTRO consensus criteria for patients "suitable" for APBI 1:
- Age ≥50 years (patient is 55 years old) 1, 2
- Invasive ductal carcinoma ≤2 cm (T1 disease; patient has 1.8 cm tumor) 1, 2
- Negative margins by ≥2 mm (patient meets this criterion) 1, 2
- Hormone receptor-positive (patient is ER-positive) 1, 2
- Node-negative disease (N0) 1, 2
- Unifocal disease (patient has unifocal tumor) 2
The European Society for Medical Oncology 2024 guidelines further support APBI for patients with tumor size ≤3 cm, which this patient clearly meets 2.
Recommended APBI Regimens
Two evidence-based treatment options are available 1, 2, 3:
Brachytherapy approach:
External beam radiation therapy approach:
Both regimens target the tumor bed and are delivered over approximately 5-8 days 4.
Evidence Supporting APBI in This Population
Non-inferiority has been demonstrated: A randomized study of APBI using interstitial brachytherapy versus whole breast radiation therapy showed APBI was not inferior to WBRT with respect to 5-year local control, disease-free survival, and overall survival 1. The RAPID trial confirmed non-inferiority with 8-year cumulative ipsilateral breast tumor recurrence rates of 3.0% for APBI versus 2.8% for whole breast irradiation (HR 1.27,90% CI 0.84-1.91) 4.
Long-term outcomes are favorable: The NSABP B-39 trial demonstrated 10-year IBTR rates of 4.6% with APBI versus 3.9% with whole breast irradiation, with overall low recurrence rates in both arms 5.
Important Caveats
Cosmetic outcomes require attention to technique: The RAPID trial showed increased late toxicity and worse cosmesis with twice-daily external beam APBI (17.7% adverse cosmesis at 7 years) 4, 5. This appears related to the twice-daily fractionation schedule 4, 5.
Alternative fractionation schemes may improve outcomes: Once-daily APBI regimens are under investigation and may provide better cosmetic results 1, 5. A novel once-daily scheme of 49.95 Gy in 15 fractions demonstrated 93.5% 12-year ipsilateral breast recurrence-free survival with 91% excellent-to-good cosmesis 6.
Brachytherapy may offer superior cosmesis: Interstitial brachytherapy showed similar toxicity profiles and cosmetic results to whole breast irradiation at 5 years, with fewer grade 2/3 late skin side effects 1. The American Brachytherapy Society identifies interstitial brachytherapy as having the strongest evidence among APBI techniques 7.
Ensure complete target coverage: Any APBI technique must allow full coverage of the entire target volume, typically 1-1.5 cm beyond the surgical cavity 2, 8. CT-based treatment planning is essential 3.
Clinical Trial Participation
While APBI is now guideline-endorsed for suitable patients like this one, the NCCN still encourages participation in high-quality prospective clinical trials when available, as some aspects remain investigational 1, 3.