EORTC/ESTRO defined induced oligopersistence of liver metastases from colorectal cancer - outcomes and toxicity profile of computer tomography guided high-dose-rate brachytherapy.

Colorectal cancer (CRC) often leads to liver metastases, which may be resistant to systemic therapy. This study assessed outcomes and toxicity of computed tomography (CT) guided high-dose-rate (HDR) brachytherapy (BRT) in oligopersistent liver metastases from CRC. The study included patients with liver metastases classified as EORTC/ESTRO-defined induced oligopersistence after multiple systemic therapy lines. Up to four persistent liver metastases per patient were treated with CT-guided brachytherapy (CT-BRT). Treatment response was evaluated using the Response Evaluation Criteria in Solid Tumors (RECIST 1.1). The analysis focused on overall survival (OS), progression-free survival (PFS), tumor burden score (TBS), and the prognostic value of changes in metastasis size. Sixty-eight CRC patients were enrolled. During a median follow-up of 17 months, the median OS was 16 months, and the median PFS was 13 months. Complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD) were observed in 7%, 35%, 44%, and 6% of patients, respectively. Patients with an objective response (ORR) of 42% had longer OS and PFS than those without it. OS was affected by lymph node metastases and metastasis size reduction, while PFS was additionally influenced by the administered dose. Multivariate analysis showed OS was linked to lymph node metastases (p = 0.001) and ORR (p = 0.004), and PFS to tumor burden score (TBS) difference (p = 0.017) and post-CT-BRT single metastasis size (p = 0.026). CT-BRT for CRC oligopersistent liver metastases is effective, improving PFS and OS, with TBS difference identified as a key response parameter for future strategies.