Image-guided intensity-modulated radiation therapy for gallbladder carcinoma

Purpose: Clinical and technical parameter analysis of patients treated with ultrasound-based image-guided tomotherapeutic IMRT for gallbladder cancer. Methods and materials: Between 8/2001 and 5/2005, 10 patients with primary tumors of the gallbladder were treated by image-guided IMRT to median doses of 59 Gy. To analyze normal tissue radiation exposure reduction using this novel approach, a virtual plan comparison between actually delivered IMRT plans and re-computed plans with identical inverse planning parameters but more conventional PTV safety margins was conducted. Results: Average CTV was 379 cm³, with a mean initial PTV of 834 cm³. In 9/10 patients, a boost was delivered to a mean CTV_boost of 171 cm³ and average PTV_boost of 241 cm³. One patient reported RTOG grade 3 acute toxicity. All other patients exhibited Grade 2 or lower acute toxicity. Preliminary median overall survival was 16.7 months (range 3.2-34.9 months), with 5/10 patients alive at analysis. Virtual plan comparison revealed significant organ-at-risk sparing by the enabled PTV margin reduction. Conclusion: Ultrasound-based image-guided IMRT is a feasible mechanism of delivering conformal radiation doses to tumors of the gallbladder with acceptable toxicity. Early outcome data with this novel radiation planning and delivery technique are encouraging and comparable to previously reported literature.