Long-term outcomes of accelerated partial breast irradiation with multicatheter interstitial brachytherapy versus whole breast irradiation: an 11-Year clinical practice follow-up study.

Purpose: To compare the long-term outcomes of accelerated partial breast irradiation (APBI) using multicatheter interstitial brachytherapy versus whole breast irradiation (WBI), in terms of late toxicity, cosmetic results, quality of life, and survival, in a real-world clinical setting.

Methods: Updated analysis of two prospectively collected cohorts comprising 76 patients with stage I-II breast cancer treated with breast-conserving surgery followed by adjuvant radiotherapy. Patients who underwent APBI met the GEC-ESTRO eligibility criteria. We assessed follow-up and additional analyses of late toxicity, quality of life (assessed using the validated QLQ-BR23 and S-BIS questionnaires), cosmetic outcomes (via Visual Analog Scale), overall survival (OS), and disease-free survival (DFS), providing a more comprehensive evaluation of long-term outcomes.

Results: At a median follow-up of 11 years, patient-reported quality of life remained significantly better in the APBI group, particularly in both physical and psychological domains, consistent with previous findings. No significant differences were observed in late clinical toxicity or cosmetic outcomes between groups. However, late mammographic findings showed a higher incidence of architectural distortion and tissue retraction in the APBI group, confirming earlier observations. The estimated 5- and 10-year OS rates were 94.7 and 81.1%, respectively. Corresponding DFS rates were 92.1% and 79.7%, with no statistically significant differences between treatment groups.

Conclusion: With extended follow-up, our results reinforce that APBI using multicatheter interstitial brachytherapy is a safe and effective alternative to WBI in selected patients, providing long-term tumor control and survival comparable to WBI, while offering improved quality of life.