A randomised study of the use of a customised immobilisation system in thetreatment of prostate cancer with conformal radiotherapy

Purpose: To evaluate the impact of a customised immobilisation system on fi eld placement accuracy, simulation and treatment delivery rime, radiographe r convenience and patient acceptability. Patients and methods: Thirty men receiving radical radiotherapy for prostat e cancer were randomised using a cross over trial design to have radiothera py planning and treatment given either in a conventional treatment position (CTP) or using an immobilisation system (LMS). The randomisation was to ha ve either the CTP or IMS for the initial 3 weeks of radiotherapy after whic h patients were replanned and changed to the alternative treatment set-up. Treatment accuracy was measured using an electronic portal imaging device. Radiographers and patients completed weekly questionnaires. Results: Median simulation time was 22.5 min (range 20-30 min) in the CTP a nd 25 min (range 15-40 min) for the IMS (P < 0.001). Median treatment time was 9 min for CTP (range 8-10 min), and 10 min (range 8.5-13.5 min) for IMS (P < 0.001). Median isocentre displacement for anterior fields was 1.7 mm from the simulated isocentre for the CTP compared to 2.0 mm for IMS (P = 0. 07). For left lateral fields values were 1.8 and 1.8 mm (P = 0.98), and for right lateral fields 2.1 and 1.7 mm (P = 0.06), respectively. No clinicall y significant reduction in either systematic or random field placement erro rs was demonstrated. Radiographers reported that patients found the IMS mor e comfortable than CTP (P < 0.001), but when using the IMS, they noticed gr eater difficulty in patient positioning (P < 0.001), and alignment to skin tattoos (P < 0.001). Conclusions: Although IMS may have been more comfortable, treatment accurac y was not improved compared to the CTP in our department. In addition, trea tment look longer and patient set-up was more difficult. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.