Comparative Analysis of Oncological Efficacy and Cosmetic Outcomes of Accelerated Partial Breast Irradiation Techniques: Multicatheter Interstitial Brachytherapy and Conformal External Beam Radiotherapy

Accelerated partial breast irradiation (APBI) is a standard radiotherapy approach for patients with early-stage breast cancer. Various techniques can be employed to deliver APBI, with external beam radiotherapy (EBRT) and interstitial high-dose-rate brachytherapy (HDR-BT) using an Ir-192 source being the most commonly used in clinical practice. Purpose: To compare the oncological efficacy and cosmetic outcomes in breast cancer patients treated with postoperative APBI using either HDR-BT or EBRT. The primary efficacy endpoints were ipsilateral breast tumor recurrence-free survival (IBTR-FS) and recurrence-free survival (RFS). Materials and Methods: Between 2016 and 2022, 183 patients with рТ_1-2N₀M₀ breast cancer underwent APBI to the tumor bed after breast-conserving surgery. In the APBI-EBRT group (n = 85), irradiation was delivered in 10 fractions of 3.85 Gy (total equivalent dose   (α/β = 3) — 52 Gy). In the APBI-HDR-BT group (n = 98), we delivered 8 fractions of 4 Gy over 4 days (two fractions per day with >6-hour   intervals, total equivalent dose (α/β = 3) — 50 Gy). All patients met the GEC-ESTRO criteria for APBI. Cosmetic outcomes were assessed at 3 and 5 years post-treatment via a standardized telephone interview using six items from the BREAST-Q questionnaire. Responses were summed into a score (range: 6–18) and categorized as ‘excellent’, ‘good’, ‘satisfactory’, or ‘unsatisfactory’. Results: The median follow-up was 45 months in the APBI-EBRT group and 70 months in the APBI-HDR-BT group. The 3-year IBTR-FS was 100 % in both groups. The 3-year RFS was 97.6 % in the APBI-EBRT group and 98.0 % in the APBI-HDR-BT group (p = 1.0). In the   APBI-HDR-BT group, the 5-year IBTR-FS and RFS rates were 95.1 % and 93.9 %, respectively.   The 3-year cosmetic assessment revealed an ‘excellent’ result in 49 of 54 patients (90.7 %) in the APBI-EBRT group, while all 53 patients (100 %) in the APBI-HDR-BT group reported an ‘excellent’ result (p = 0.059). At the 5-year assessment, an ‘excellent’ cosmetic outcome was maintained in all patients in the APBI-HDR-BT group. Conclusion: Both APBI techniques (HDR-BT and EBRT) demonstrated comparably high efficacy in terms of local control after 3-year of follow-up. However, APBI delivered with HDR-BT showed a trend towards more favorable long-term cosmetic outcomes compared to APBI delivered with EBRT.

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