E Raggi1, M A Mosleh-Shirazi, F H Saran. 1. Department of Radiotherapy and Paediatric Oncology, Royal Marsden NHS Foundation Trust, Sutton, Surrey SM2 5PT, UK.
Abstract
AIMS: To evaluate different treatment techniques in whole ventricular radiotherapy (WVRT) for localised intracranial germinomas with respect to target volume and organ at risk (OAR) dose. As a second end point, a comparison of OAR doses between WVRT and whole brain radiotherapy was made. MATERIALS AND METHODS: Co-registered computed tomography-magnetic resonance images (MRI) of five patients were studied. Planning target volumes for whole ventricles (phase 1, PTV(1)) and boost to the primary tumour (phase 2, PTV(2)) were prescribed to 24 and 16 Gy. For phase 1, lateral parallel-opposed pairs (PP), non-coplanar three- and four-field (3F and 4F) and optimised four- and seven-field intensity-modulated radiotherapy (4FIMRT and 7FIMRT) plans were compared. A conformal non-coplanar six-field technique was used for phase 2. RESULTS: For phase 1, statistically significant high-dose sparing of normal brain was achieved with increasing treatment complexity for supratentorial brain (STB) minus PTV(1) (STB-PTV(1)) and infratentorial brain (ITB) minus PTV(1) (ITB-PTV(1)). Median pituitary gland dose sparing was 1 Gy with IMRT techniques (P=not significant). CONCLUSION: WVRT using 7FIMRT is the most conformal technique, which offers significant sparing of normal brain from high-dose irradiation, a mean reduction of 1 Gy in the pituitary gland (P<0.05) with no significant reduction in other OARs. Yet even with the most complex technique the absolute reduction in mean dose to normal brain tissue achieved was modest in clinical terms. Whether this could translate into a reduction in late sequelae in a predominantly adolescent patient population remains hypothetical.
AIMS: To evaluate different treatment techniques in whole ventricular radiotherapy (WVRT) for localised intracranial germinomas with respect to target volume and organ at risk (OAR) dose. As a second end point, a comparison of OAR doses between WVRT and whole brain radiotherapy was made. MATERIALS AND METHODS: Co-registered computed tomography-magnetic resonance images (MRI) of five patients were studied. Planning target volumes for whole ventricles (phase 1, PTV(1)) and boost to the primary tumour (phase 2, PTV(2)) were prescribed to 24 and 16 Gy. For phase 1, lateral parallel-opposed pairs (PP), non-coplanar three- and four-field (3F and 4F) and optimised four- and seven-field intensity-modulated radiotherapy (4FIMRT and 7FIMRT) plans were compared. A conformal non-coplanar six-field technique was used for phase 2. RESULTS: For phase 1, statistically significant high-dose sparing of normal brain was achieved with increasing treatment complexity for supratentorial brain (STB) minus PTV(1) (STB-PTV(1)) and infratentorial brain (ITB) minus PTV(1) (ITB-PTV(1)). Median pituitary gland dose sparing was 1 Gy with IMRT techniques (P=not significant). CONCLUSION: WVRT using 7FIMRT is the most conformal technique, which offers significant sparing of normal brain from high-dose irradiation, a mean reduction of 1 Gy in the pituitary gland (P<0.05) with no significant reduction in other OARs. Yet even with the most complex technique the absolute reduction in mean dose to normal brain tissue achieved was modest in clinical terms. Whether this could translate into a reduction in late sequelae in a predominantly adolescent patient population remains hypothetical.
Authors: Dora Correia; Dario Terribilini; Stefan Zepter; Alessia Pica; Nicola Bizzocchi; Werner Volken; Sonja Stieb; Frank Ahlhelm; Evelyn Herrmann; Michael K Fix; Peter Manser; Daniel M Aebersold; Damien C Weber Journal: Clin Transl Radiat Oncol Date: 2019-01-09