Multicatheter HDR partial-breast irradiation maintained low recurrence through 15 years

KEY POINTS

• This prospective observational Phase II study enrolled 292 patients treated between 2003 and 2023, with follow-up extending to 20 years. Eligible patients were age ≥40 years with DCIS or non-lobular invasive cancer, tumor size ≤2.5 cm, negative nodes and surgical margins ≥2 mm.
• The cohort was strongly favorable-risk: 90.8% had stage I disease, median tumor size was 10 mm, and 90.7% had hormone receptor-positive/HER2-negative tumors.
• Partial-breast irradiation was delivered using interstitial multicatheter HDR brachytherapy to 32 Gy in 8 fractions over 4 days, with two 4 Gy fractions per day separated by at least six hours.
• With a median follow-up of 102 months, ipsilateral breast recurrence occurred in 10/292 patients (3.4%). Cumulative incidence was 1.8% at 5 years and 3.8% at both 10 and 15 years, indicating little additional local failure after the first decade.
• Late toxicity was documented in 35% of evaluable patients, but all events were grade 1 or 2. The most frequent effects were telangiectasia (18.5%), fibrosis (16.4%) and fat necrosis (7.3%), with overall cumulative late toxicity remaining nearly stable between five and ten years.
• Cosmetic outcomes remained favorable. Physicians rated 95.8% of evaluable patients as having excellent or good cosmesis at last follow-up. Patient self-assessment was also favorable, with 88% reporting excellent or good outcomes.
• Breast cancer-specific survival was 98.4% at 5 years, 95.7% at 10 years and 94.0% at 15 years. Distant metastasis developed in 4.8% overall, with a cumulative incidence of 8.1% at 15 years.
• The cohort was highly selected and had no whole-breast or external-beam PBI comparator. Treatment technology also evolved substantially across the 20-year enrollment period, and historical treatment plans could not be re-reviewed to investigate the relatively frequent low-grade telangiectasia. 8 Brachy

CLINICAL TAKEAWAY

SOURCE

Brachytherapy