RESUMEN
PURPOSE: Proton therapy is highly effective for liver malignancies, and to increase its accuracy, placement of fiducial markers in the liver is preferred. We retrospectively evaluated the safety and feasibility of CT-guided fiducial marker implantation using ultra-fine 25-gauge needles before proton therapy for liver malignancies. MATERIALS AND METHODS: Between May 2016 and April 2021, 334 cases were investigated. All of procedures were performed without anesthesia. Technical success was defined as the completion of implantation at the intended site. Tumor-marker distance and possibility of synchronization between tumors and markers were evaluated and compared with Mann-Whitney U test. Complications were evaluated using the Common Terminology Criteria for Adverse Events, version 4.0. RESULTS: Technical success rate was 97.3%. Tumor-marker distance was 19.1 mm (median, range 0-96) in the group in which the implanted marker was synchronized with tumor (n = 315), while it was 34.5 mm (median, range 6-94) in the group in which the implanted marker was not synchronized (n = 13) (p value = 0.011 < 0.05). The complication rate was 2.4%, 2 were classified as grade 4 and 5 as grade 1, and 1 as grade 2. There were no grade 3 or higher complications that seemed to be related to the procedure. CONCLUSION: CT-guided marker implantation using a 25-gauge needle achieved a satisfactory success rate with few complications and was useful for the image-guided and respiratory-synchronized proton therapy. LEVEL OF EVIDENCE 3: Local non-random sample.