Clinical efficacy of CT-guided iodine-125 seed brachytherapy in unresectable locoregionally recurrent breast cancer.

Purpose: Clinical efficacy of computed tomography (CT)-guided iodine-125 (¹²⁵I) seed brachytherapy in unresectable locoregionally recurrent breast cancer.

Material and methods: A retrospective analysis was conducted on the clinical data of 68 patients with unresectable locoregionally recurrent breast cancer who underwent radioactive ¹²⁵I seed implantation therapy at our hospital between January 2018 and October 2023. All patients received CT-guided ¹²⁵I seed implantation. Postoperatively, follow-up was carried out to calculate the local control rate, monitor the occurrence of complications, and compare the serum levels of carcinoembryonic antigen (CEA) and carbohydrate antigen 153 (CA153) before and after treatment.

Results: A total of 89 locally recurrent lesions were identified in the 68 patients. The ¹²⁵I seed implantation procedure achieved a success rate of 97.75% (87/89), with a local control rate (LCR) of 88.76% (79/89) and an objective response rate (ORR) of 75.28% (67/89). Stratified by initial clinical stage, the ORR was 80.00% (20/25) in patients with stage I + II disease and 67.44% (29/43) in those with stage III + IV disease, showing a statistically significant difference (χ² = 9.822, p < 0.001). The pain relief effective rate at 1 month postoperatively was 91.18%. For the 68 patients, the median local progression-free survival (LPFS) was 25.60 months (95% confidence interval [CI]: 20.36-26.70), with 1-year, 2-year, and 3-year LPFS rates of 82.35%, 52.94%, and 17.65%, respectively. The median overall survival (OS) was 36.65 months (95% CI: 34.50-40.20), with 1-year, 2-year, and 3-year OS rates of 95.59%, 70.59%, and 51.47%, respectively. Univariate and multivariate analyses identified primary tumor stage, molecular subtype, treatment modality, and recurrence site as key factors influencing survival in locally recurrent breast cancer, with respective hazard ratios (HR) of 2.473 (p = 0.042), 1.359 (p = 0.036), 1.166 (p = 0.011), and 1.997 (p = 0.014). The median LPFS was 28.60 months in patients with initial clinical stage I + II and 20.36 months in those with stage III + IV, with a statistically significant difference (χ² = 4.567, p = 0.0326). The median LPFS was 25.95, 25.60, 20.36, and 11.55 months for patients with Luminal A, Luminal B, HER-2-positive, and triple-negative subtypes, respectively, with a statistically significant difference (χ² = 4.068, p = 0.0437). The median LPFS was 25.60 months in the 60 patients who received systemic therapy vs. 13.55 months in the 8 patients who received monotherapy alone, with a statistically significant difference (χ² = 9.170, p = 0.0025). For patients with multi-site recurrence (n = 15) and single-site recurrence (n = 53), the median LPFS was 15.60 months and 25.60 months, respectively, with a statistically significant difference (χ² = 4.060, p = 0.0439). Following ¹²⁵I seed implantation, most adverse reactions were grade 1 or 2, with an overall incidence of 36.96%, and no severe postoperative complications were observed.

Conclusions: CT-guided ¹²⁵I seed brachytherapy for locoregionally recurrent breast cancer is characterized by definite efficacy, minimal invasiveness, and fewer complications compared with external beam radiotherapy. It can serve as an important treatment option for locoregionally recurrent breast cancer, particularly in cases with poor control of localized progression-free survival, such as advanced disease, multisite recurrences, and triple-negative breast cancer, which is prone to distant metastasis.