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Purpose: The aim of this study was to provide estimates of setup and internal margins of patients treated for rectal carcinoma using helical tomotherapy and to assess possible margin adaptations. Using helical tomotherapy, highly conformal dose distributions can be created, and the integrated megavoltage computed tomography (MVCT) modality allows very precise daily patient positioning. In clinical protocols, however, margins originating from traditional setup procedures are still being applied. This work investigates whether this modality can aid in redefining treatment margins. Methods and Materials: Ten patients who were treated with tomotherapy underwent MVCT scanning before and after 10 treatments. Using automatic registration the necessary setup margin was investigated by means of bony landmarks. Internal margins were assessed by delineating and describing the mesorectal movement. Results: Based on bony landmarks, movement of patients during treatments was limited to 2.45 mm, 1.99 mm, and 1.09 mm in the lateral, longitudinal, and vertical direction, respectively. Systematic errors were limited to <1 mm. Measured movement of the mesorectal space was −1.6 mm (± 4.2 mm) and 0.1 mm (± 4.0 mm) for left and right lateral direction. In the antero-posterior direction, mean shifts were −2 mm (± 6.8 mm) and −0.4 mm (± 3.8 mm). Mean shifts in the cranio-caudal direction were respectively −3.2 mm (± 5.6 mm) and −3.2 mm (± 6.8 mm). Conclusions: The use of the integrated MVCT on the tomotherapy system can minimize the setup margin for rectal cancer, and can also be used to adequately describe the internal margin allowing for direct treatment margin adaptation. [Copyright &y& Elsevier]

Purpose: To evaluate early side effects in prostate cancer patients treated with image-guided conformation arc therapy (IGCAT) using a minimultileaf collimator and daily X-ray–assisted patient positioning. Methods and Materials: Between May 2000 and November 2004, 238 cT1-T3N0M0 tumors were treated with doses of 70 or 78 Gy. Seventy patients also received neoadjuvant or concurrent hormonal treatment. Median follow-up is 18 months (range, 4–55 months). The Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer toxicity scoring system was used to evaluate early side effects. Results: Grade 1, 2, and >2 acute side effects occurred in 19, 6, and 0% (gastrointestinal) and 37, 16, and 0% (genitourinary) of the patients. No relation between radiation dose and early side effects was observed. Conclusion: Patients treated with image-guided conformation arc therapy experience a low rate of Grade 2 (i.e., requiring medication) early side effects. The definitive evaluation of late side effects and biochemical control requires further follow-up. [Copyright &y& Elsevier]