Uffe Bernchou1, Trine Skak Tranemose Arnold2, Brit Axelsen3, Mette Klüver-Kristensen3, Faisal Mahmood4, Frederik Severin Gråe Harbo5, Jon Thor Asmussen5, Olfred Hansen6, Anders Smedegaard Bertelsen3, Steinbjørn Hansen6, Carsten Brink4, Rikke Hedegaard Dahlrot6. 1. Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense, Denmark; Department of Clinical Research, University of Southern Denmark, Odense, Denmark. Electronic address: uffe.bernchou@rsyd.dk. 2. Department of Oncology, Odense University Hospital, Odense, Denmark. 3. Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense, Denmark. 4. Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense, Denmark; Department of Clinical Research, University of Southern Denmark, Odense, Denmark. 5. Department of Radiology, Odense University Hospital, Odense, Denmark. 6. Department of Clinical Research, University of Southern Denmark, Odense, Denmark; Department of Oncology, Odense University Hospital, Odense, Denmark.
Abstract
BACKGROUND AND PURPOSE: Tumour growth during radiotherapy may lead to geographical misses of the target volume. This study investigates the evolution of the tumour extent and evaluates the need for plan adaptation to ensure dose coverage of the target in glioblastoma patients. MATERIALS AND METHODS: The prospective study included 29 patients referred for 59.4 Gy in 33 fractions. Magnetic resonance imaging (MRI) was performed at the time of treatment planning, at fraction 10, 20, 30, and three weeks after the end of radiotherapy. The gross tumour volume (GTV) was defined as the T1w contrast-enhanced region plus the surgical cavity on each MRI set. The relative GTV volume and the maximum distance (Dmax) of the extent of the actual GTV outside the original GTV were measured. Based on the location of the actual GTV during radiotherapy and the original planned dose, a prospective clinical decision was made whether to adapt the treatment. RESULTS: Dose coverage of the GTV during radiotherapy was not compromised, and none of the radiotherapy plans was adapted. The median Dmax (range) was 5.7 (2.0-18.9) mm, 8.0 (2.0-27.4) mm, 8.0 (1.9-27.3) mm, and 8.9 (1.9-34.4) mm at fraction 10, 20, 30, and follow-up. The relative GTV volume and Dmax observed at fraction 10 were correlated with the values observed at follow-up (R=0.74, p<0.001 and R=0.79, p<0.001, respectively). CONCLUSION: Large variations in the GTV extent were observed, and changes often occurred early in the treatment. Plan adaptation for geographical misses was not performed in our cohort due to sufficient CTV margins.
BACKGROUND AND PURPOSE:Tumour growth during radiotherapy may lead to geographical misses of the target volume. This study investigates the evolution of the tumour extent and evaluates the need for plan adaptation to ensure dose coverage of the target in glioblastomapatients. MATERIALS AND METHODS: The prospective study included 29 patients referred for 59.4 Gy in 33 fractions. Magnetic resonance imaging (MRI) was performed at the time of treatment planning, at fraction 10, 20, 30, and three weeks after the end of radiotherapy. The gross tumour volume (GTV) was defined as the T1w contrast-enhanced region plus the surgical cavity on each MRI set. The relative GTV volume and the maximum distance (Dmax) of the extent of the actual GTV outside the original GTV were measured. Based on the location of the actual GTV during radiotherapy and the original planned dose, a prospective clinical decision was made whether to adapt the treatment. RESULTS: Dose coverage of the GTV during radiotherapy was not compromised, and none of the radiotherapy plans was adapted. The median Dmax (range) was 5.7 (2.0-18.9) mm, 8.0 (2.0-27.4) mm, 8.0 (1.9-27.3) mm, and 8.9 (1.9-34.4) mm at fraction 10, 20, 30, and follow-up. The relative GTV volume and Dmax observed at fraction 10 were correlated with the values observed at follow-up (R=0.74, p<0.001 and R=0.79, p<0.001, respectively). CONCLUSION: Large variations in the GTV extent were observed, and changes often occurred early in the treatment. Plan adaptation for geographical misses was not performed in our cohort due to sufficient CTV margins.