KEY POINTS
- Randomized evidence supports brachytherapy-based accelerated partial-breast irradiation in appropriately selected patients. In the GEC-ESTRO phase III trial, 10-year local recurrence was 3.51% with multicatheter APBI versus 1.58% with whole-breast irradiation, while excellent patient-reported cosmesis was more common after APBI (45% vs 34%).
- Patient-selection recommendations differ across ABS, GEC-ESTRO, and ASTRO, but broadly favour node-negative early breast cancer with negative margins. The 2024 ASTRO guideline strongly supports APBI for patients aged ≥40 years with grade 1–2, estrogen receptor-positive tumours measuring ≤2 cm, while positive nodes, positive margins, known BRCA1/2 mutations, and age below 40 remain contraindications.
- Implant feasibility depends on clear visualization of the lumpectomy cavity on thin-slice CT, supported by seroma, surgical clips, operative findings, and pathology. Extensive oncoplastic rearrangement may make the true tumour bed unreliable, while an ideal expanded target volume is generally below approximately 150 cm³.
- Multicatheter interstitial implants can accommodate almost any target shape and typically use three catheter planes, spaced approximately 1–1.5 cm apart, with around 12–18 catheters for a freehand implant. Figures 1 and 3 illustrate favourable cavity anatomy and the recommended sequence of deep, superficial, and intermediate catheter placement.
- Single-entry devices require a simple cavity that matches the applicator geometry. A single-channel balloon generally requires a skin bridge of approximately 1 cm, whereas multilumen balloons may be used with 3–5 mm spacing and strut-based devices can sometimes accommodate less than 3 mm, provided dose constraints remain acceptable.
- Postimplant CT should cover the entire breast with slice thickness ≤2 mm and no gaps. Wire markers are particularly important for multicatheter and SAVI reconstruction because visible struts do not necessarily represent the actual source path; inaccurate reconstruction or channel identification can invalidate all subsequent optimization.
- Common HDR schedules include 34 Gy in 10 twice-daily fractions and the shorter TRIUMPH-T regimen of 22.5 Gy in three fractions. Baseline planning goals include PTV_EVAL V90 above 90%, interstitial dose-homogeneity index ≥0.75, and technique-specific limits for V150, V200, skin, and rib dose; device position and integrity should be verified before every fraction.
CLINICAL TAKEAWAY
Breast brachytherapy remains a highly conformal APBI option with mature randomized outcome data, but its quality is strongly operator- and geometry-dependent. The paper provides a useful implementation framework for centres maintaining or developing multicatheter and single-entry programmes, while emphasizing that hands-on training cannot be replaced by written guidance alone.