Computed tomography guided high dose rate brachytherapy for induced oligoprogression of colorectal cancer liver metastases

Data on the efficacy of computer tomography guided brachytherapy (CT-BRT) for limited liver metastases is lacking; to assess CT-BRT's role in inducedoligoprogression in colorectal cancer (CRC), we performed a retrospective cohort study on CRC patients with metastatic disease, treated with 2-5 lines of systemic therapy, who achieved induced oligoprogression with up to four liver metastases eligible for CTBRT. In 75 patients, median overall survival (mOS) was 17 months, and median progression-free survival (mPFS) was 10 months during a 16-month follow-up. The mOS was not dose-dependent. Complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD) were found in 8, 31, 47, and 15%, respectively. The mOS in patients with CR, PR, SD, and PD was 23, 17, 14, and 11 months, respectively. Disease Control Rate (DCR) with a high dose influenced OS, while PFS was impacted by extrahepatic metastases (especially in abdominal/pelvic lymph nodes), the number of metastases, and DCR with a high dose. Treatment toxicity was very low (Grade 3-1%, > Grade 3-0%). We report the largest cohort demonstrating CT-BRT as an effective local treatment for colorectal liver metastases in induced oligoprogression, with minimal toxicity.