The effectiveness and prognostic factors of radioactive iodine-125 seed implantation for the treatment of cervical lymph node recurrence of esophageal squamous cell carcinoma after external beam radiation therapy

Purpose
To analyze factors influencing the efficacy of ¹²⁵I seed implantation in the treatment of in-field cervical lymph node recurrence of esophageal squamous cell carcinoma (ESCC) after external beam radiation therapy.

Material and methods
We conducted a retrospective review of 36 patients with in-field cervical metastatic lymph nodes recurrence of esophageal squamous cell carcinoma (CML-ESCC) after external beam radiation therapy treatment, who underwent ¹²⁵I seed implantation in our department from 2013 to 2019. Previous cumulative external irradiation dose ranged from 20 to 66 Gy (median, 60 Gy). The post-implant efficacy was evaluated by response evaluation criteria in solid tumors (RECIST) version 1.1, and an adverse event was evaluated by the Radiation Therapy Oncology Group (RTOG)/European Organization for Research and Treatment of Cancer Late Radiation Morbidity Score (EORTC). COX proportional hazards model was used to analyze risk factors affecting effectiveness.

Results
Among 36 patients, 31 patients (86.1%) received fluorouracil-based chemotherapy (1-6 cycles) after ¹²⁵I seed implantation. Local control rates at 3, 6, 12, and 24 months after implantation were 51%, 30%, 30%, and 18%, respectively, with a median of 9 months (95% CI: 6.106-11.894); survival rates after 3, 6, 12, and 24 months were 55%, 41%, 22%, and 22%, respectively, with a median of 8 months (95% CI: 5.753-10.247). Multivariate analysis showed that D90 and short-term efficacy were independent factors related to local control and survival rate (p = 0.005, < 0.001, 0.010, < 0.001). There were 2 cases (5.6%) with grade 1 skin toxicity, 1 case (2.8%) with grade 4 skin toxicity, 3 cases (8.3%) with grade 1 mucosal ulcer, and 3 cases (8.3%) with grade 1 xerostomia.

Conclusions
¹²⁵I seed implantation as an effective salvage treatment shows definite efficacy and safety for patients with in-field cervical lymph node recurrence of ESCC after external beam radiation therapy.