Purpose
Dose, fractionation, normalization and the dose profile inside the target volume vary substantially in pulmonary stereotactic body radiotherapy (SBRT) between different institutions and SBRT technologies. Published planning studies have shown large variations of the mean dose in planning target volume (PTV) and gross tumor volume (GTV) or internal target volume (ITV) when dose prescription is performed to the PTV covering isodose. This planning study investigated whether dose prescription to the mean dose of the ITV improves consistency in pulmonary SBRT dose distributions.
Materials and methods
This was a multi-institutional planning study by the German Society of Radiation Oncology (DEGRO) working group Radiosurgery and Stereotactic Radiotherapy. CT images and structures of ITV, PTV and all relevant organs at risk (OAR) for two patients with early stage non-small cell lung cancer (NSCLC) were distributed to all participating institutions. Each institute created a treatment plan with the technique commonly used in the institute for lung SBRT. The specified dose fractionation was 3 × 21.5 Gy normalized to the mean ITV dose. Additional dose objectives for target volumes and OAR were provided.
Results
In all, 52 plans from 25 institutions were included in this analysis: 8 robotic radiosurgery (RRS), 34 intensity-modulated (MOD), and 10 3D-conformal (3D) radiation therapy plans. The distribution of the mean dose in the PTV did not differ significantly between the two patients (median 56.9 Gy vs 56.6 Gy). There was only a small difference between the techniques, with RRS having the lowest mean PTV dose with a median of 55.9 Gy followed by MOD plans with 56.7 Gy and 3D plans with 57.4 Gy having the highest. For the different organs at risk no significant difference between the techniques could be found.
Conclusions
This planning study pointed out that multiparameter dose prescription including normalization on the mean ITV dose in combination with detailed objectives for the PTV and ITV achieve consistent dose distributions for peripheral lung tumors in combination with an ITV concept between different delivery techniques and across institutions.
~I4o KLINISCHE WOCHENSCHRiFT. r. jAHR~ANG. Nr. 4) ~i, O~ZTOBER x9~ der sie keine Tetaniesymptome mehr boten, durch willkfirliche Uberventilation wieder Tetaniesymptome ausl6sen. Ubrigens lassen sich in derselben Art bei den meisten gesunden Menschen mehr oder weniger deutliche Tetaniezeichen erzeugen, wie wit gegentiber CURSCH~ANN in Ubereinstimmung mit GRAtCT und GOLD-MAN, FREUDENBERG und GYORGu FRANK behaupten m/issen. Die neurotische Atmungstetanie ist ein keineswegs seltenes Ereignis, denn wit haben seit unserer Mitteilung weitere 3 F/ille beobachtet. Wir konnten weiter eine neue Gruppe hierher geh6riger Erscheinungen aufstellen: Patienten mit einem Vitium cordis (alle bisher beobachteten F/tile hatten eine Mitralinsuffizienz und eine Arythmia perpetua) zeigten mit beginnender Dekompeusution des Herzens unter dem Geftihle der Beklemmung und Atemnot Uberventilation und leichte Tetaniezeichen, die mit Nachlassen der Beklemmungsgeffihle und AufhSren der Uberventilation verschwanden. KURZE WISSENSCHAFT UNTERSUCHUNGEN 0BER GEFASSVERENGERNDE STOFFE IM BLUTE.
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