Phase II Study of Dose-Escalated and Convergent Stereotactic Body Radiotherapy for Liver and Pulmonary Oligometastases from Colorectal Cancer

PURPOSE: Surgical resection of liver or pulmonary oligometastases (LP-OMD) in colorectal cancer (CRC) has been shown to improve survival. Stereotactic body radiotherapy (SBRT) is a promising alternative for patients with primary lung cancer. However, the efficacy of SBRT for LP-OMD in CRC remains inconclusive, and local control (LC) rates are often unsatisfactory. This prospective study aimed to evaluate the treatment outcomes of dose-escalated and convergent SBRT for patients with LP-OMD from CRC, with the goal of demonstrating its effectiveness as a treatment option for these patients. METHODS AND MATERIALS: This study included 23 CRC patients with LP-OMD who received SBRT between 2017 and 2022. The inclusion criteria were histologically confirmed colorectal adenocarcinoma, one to three oligometastases, and a tumor diameter of 5 cm or less. Patients who were inoperable or declined surgery were included. SBRT was delivered with total doses of 50-60 Gy administered over five fractions, covering the planning target volume surface within the 60% isodose line of the maximum dose. The primary endpoint was the 2-year LC rate, while secondary endpoints included overall survival (OS), progression-free survival (PFS), and toxicity. RESULTS: The median follow-up duration was 41.0 months (range: 11.5-77.2). At the time of analysis, five patients had died from CRC, six were alive with disease, and twelve were alive without disease. Only one patient experienced local recurrence of a pulmonary oligometastasis. The 2-year LC, PFS, and OS rates were 95.0% (95% CI: 69.5-99.3), 61.3% (95% CI: 40.0-77.0), and 88.1% (95% CI: 67.6-96.0), respectively. Toxicity was acceptable, with no grade ≥ 3 adverse events. CONCLUSIONS: High-central-dose SBRT for LP-OMD from CRC achieved favorable local control with minimal toxicity. These findings should be interpreted cautiously and require validation in larger, multi-institutional studies.