LETTER • OPEN ACCESSFirst patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, highfield MRI guided radiotherapy treatment AbstractThe integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery. The proof of concept of this device was given in 2009 by demonstrating simultaneous irradiation and MR imaging on phantoms, since then the device has been further developed and commercialized by Elekta. The aim of this work is to demonstrate the clinical feasibility of online, high-precision, high-field MRI guidance of radiotherapy using the first clinical prototype MRI-Linac.Four patients with lumbar spine bone metastases were treated with a 3 or 5 beam step-and-shoot IMRT plan. The IMRT plan was created while Letter Institute of Physics and Engineering in MedicineOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. 3 Author to whom any correspondence should be addressed. the patient was on the treatment table and based on the online 1.5 T MR images; pre-treatment CT was deformably registered to the online MRI to obtain Hounsfield values. Bone metastases were chosen as the first site as these tumors can be clearly visualized on MRI and the surrounding spine bone can be detected on the integrated portal imager. This way the portal images served as an independent verification of the MRI based guidance to quantify the geometric precision of radiation delivery. Dosimetric accuracy was assessed post-treatment from phantom measurements with an ionization chamber and film. Absolute doses were found to be highly accurate, with deviations ranging from 0.0% to 1.7% in the isocenter. The geometrical, MRI based targeting as confirmed using portal images was better than 0.5 mm, ranging from 0.2 mm to 0.4 mm.In conclusion, high precision, high-field, 1.5 T MRI guided radiotherapy is clinically feasible.

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For laryngohypopharyngeal tumors, 45-52% target volume reduction compared with CTV is achievable when modality-specific CTV margins are used. PET-based CTVs were significantly smaller compared to CT- and MRI-based CTVs.

Pain response after conventional external beam radiation therapy (cRT) in patients with painful bone metastases is observed in 60% to 70% of patients. The aim of the VERTICAL trial was to investigate whether stereotactic body radiation therapy (SBRT) improves pain response. Methods and Materials: This single-center, phase 2, randomized controlled trial was conducted within the PRESENT cohort, which consists of patients referred for radiation therapy of bone metastases to our tertiary center. Cohort participants with painful bone metastases who gave broad informed consent for randomization were randomly assigned to cRT or SBRT. Only patients in the intervention arm received information about the trial and were offered SBRT (1 Â 18 Gy, 3 Â 10 Gy, or 5 Â 7 Gy), which they could accept or refuse. Patients who refused SBRT underwent standard cRT (1 Â 8 Gy, 5 Â 4 Gy, or 10 Â 3 Gy). Patients in the control arm were not informed. Primary endpoint was pain response at 3 months after radiation therapy.

BACKGROUNDIn this prospective study, the effects of a second course of postoperative radiation therapy on locoregional control, survival, toxicity, and quality of life were investigated in patients who underwent resection of a second primary or locoregional recurrent head and neck tumor in a previously irradiated area.METHODSIn total, 39 patients who underwent surgery for second primary tumors (n = 19 patients) or for recurrent locoregional tumors (n = 20 patients) were retreated with postoperative radiotherapy (RE‐PORT). Indications for RE‐PORT were extranodal spread (49%), positive surgical margins (44%), and/or other risk factors (8%). The target volume for RE‐PORT was confined to the high‐risk area. No elective radiotherapy was applied in regions that were situated in the formerly high‐dose area. A total dose of 46 grays (Gy) was given to elective areas with boosts from 60 Gy to 66 Gy to the high‐risk region with conventional fractionation. The results of RE‐PORT were compared with the results from patients who were treated in the same period with primary adjuvant radiotherapy (PRI‐PORT) at the authors' institution.RESULTSThe mean follow‐up was 32 months (range, 3‐84 mos). The locoregional control rate after 3 years in the RE‐PORT group was 74%, and the 3‐year overall survival rate was 44%. This did not differ significantly compared with survival rates in the PRI‐PORT group. Although a higher rate of late radiation‐induced morbidity and more head and neck symptoms were observed in the RE‐PORT group compared with the PRI‐PORT group, no differences were observed with regard to the more general dimensions of quality of life.CONCLUSIONSRE‐PORT after surgery for recurrent locoregional tumors and/or second primary tumors should be considered in patients who have high‐risk histopathologic features. Cancer 2006. © 2006 American Cancer Society.