Simon Wagenblast1,2, Severin Kampfer1, Kai J Borm1, Stephanie E Combs1,3,4, Steffi U Pigorsch1,3, Marciana-Nona Duma5,6,7. 1. Department of Radiation Oncology, Klinikum rechts der Isar, Technical University Munich, Ismaninger Straße 22, 81675, Munich, Germany. 2. Faculty of Medicine, Technical University, Munich, Germany. 3. Deutsches Konsortium für Translationale Krebsforschung (DKTK)-Partner Site Munich, Munich, Germany. 4. Institute of Innovative Radiotherapy, Helmholtzzentrum München, Munich, Germany. 5. Department of Radiation Oncology, Klinikum rechts der Isar, Technical University Munich, Ismaninger Straße 22, 81675, Munich, Germany. Marciana.Duma@tum.de. 6. Deutsches Konsortium für Translationale Krebsforschung (DKTK)-Partner Site Munich, Munich, Germany. Marciana.Duma@tum.de. 7. Institute of Innovative Radiotherapy, Helmholtzzentrum München, Munich, Germany. Marciana.Duma@tum.de.
Abstract
BACKGROUND: The goal of this study was to investigate if daily dose recalculations are necessary or if less time-consuming approaches can be used to identify dose differences to the planned dose in patients with head and neck cancers (H&N). METHODS: For 12 H&N patients treated with helical tomotherapy, daily dose calculations were performed retrospectively. Four different summation doses (SuDo) were calculated: DayDo (daily dose calculation), MVCTx2, MVCTx5, and MVCTx10 (dose calculations every second, fifth, and tenth fraction). Dose recalculations were depicted on the last contoured mega voltage CT (MVCT). The DayDo was compared to the planned dose and to the less time-consuming SuDo scenarios. The doses were assessed for the planning target volume (PTV) and the organs at risk (OARs): mandible (mand), spinal cord (SC), spinal cord +5 mm (SC+5 mm), parotid glands (PG). RESULTS: The ipsilateral PG, contralateral PG, and PTV volume decreased by -22.5% (range: -34.8 to 5.2%), -19.5% (-31.5 to 15.8%), and -2.6% (-16.7 to 0.2%), respectively. There was a significant median mean dose (Dmean) dose difference for DayDo compared to the planned dose for PG total of 1.9 Gy (-3.3 to 7.3 Gy). But less time-consuming SuDo compared to DayDo showed statistically significant but not clinically relevant (<2%) dose differences for several organs. Hence the small dose difference to the gold standard (DayDo), we recommend dose recalculations every fifth MVCT in order to identify the occurrence of dose differences compared to the planned dose. CONCLUSION: Daily dose calculations are the most precise to assess dose differences between actual and planned dose. Dose recalculations on every fifth MVCT (i. e., weekly control CTs) are an applicable and time-saving way of identifying patients with significant dose differences compared to the planned dose.
BACKGROUND: The goal of this study was to investigate if daily dose recalculations are necessary or if less time-consuming approaches can be used to identify dose differences to the planned dose in patients with head and neck cancers (H&N). METHODS: For 12 H&N patients treated with helical tomotherapy, daily dose calculations were performed retrospectively. Four different summation doses (SuDo) were calculated: DayDo (daily dose calculation), MVCTx2, MVCTx5, and MVCTx10 (dose calculations every second, fifth, and tenth fraction). Dose recalculations were depicted on the last contoured mega voltage CT (MVCT). The DayDo was compared to the planned dose and to the less time-consuming SuDo scenarios. The doses were assessed for the planning target volume (PTV) and the organs at risk (OARs): mandible (mand), spinal cord (SC), spinal cord +5 mm (SC+5 mm), parotid glands (PG). RESULTS: The ipsilateral PG, contralateral PG, and PTV volume decreased by -22.5% (range: -34.8 to 5.2%), -19.5% (-31.5 to 15.8%), and -2.6% (-16.7 to 0.2%), respectively. There was a significant median mean dose (Dmean) dose difference for DayDo compared to the planned dose for PG total of 1.9 Gy (-3.3 to 7.3 Gy). But less time-consuming SuDo compared to DayDo showed statistically significant but not clinically relevant (<2%) dose differences for several organs. Hence the small dose difference to the gold standard (DayDo), we recommend dose recalculations every fifth MVCT in order to identify the occurrence of dose differences compared to the planned dose. CONCLUSION: Daily dose calculations are the most precise to assess dose differences between actual and planned dose. Dose recalculations on every fifth MVCT (i. e., weekly control CTs) are an applicable and time-saving way of identifying patients with significant dose differences compared to the planned dose.
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