High-intensity focused ultrasound treatment of late-stage pancreatic body carcinoma: optimal tumor depth for safe ablation.

Objective criteria are currently not available for assessing the extent of ablation by high-intensity focused ultrasound (HIFU). A retrospective review was conducted in Chinese patients with late-stage pancreatic body carcinoma treated with 1 h/d intermittent HIFU at a single center. Clinical and procedure-related characteristics were examined in relation to tumor posterior depth. Clinically, tumor ablation was negatively correlated with posterior tumor depth, with a 1-cm increase in depth decreasing ablation by 30.7%. At a computed tomography (CT)-determined 7-cm posterior tumor depth (considered the critical value for the procedure), ablation sensitivity and specificity were 77.8% and 72.7%, respectively. Tumor ablation >30% in patients with a CT-determined posterior tumor depth ≤7 cm was 9.333 times better than that in patients with a CT-determined posterior tumor depth >7 cm. Adverse effects did not affect the efficacy of HIFU. Tumors with posterior depths <7 cm may effectively be treated with HIFU-induced ablation with minimal adverse events.