ABSTRACT
To analyse the pattern of recurrence of patients treated with Stupp protocol in relation to technique, to compare in silico plans with reduced margin (1 cm) with the original ones and to analyse toxicity. 105 patients were treated: 85 had local recurrence and 68 of them were analysed. Recurrence was considered in field, marginal and distant if >80 %, 20-80 % or <20 % of the relapse volume was included in the 95 %-isodose. In silico plans were retrospectively recalculated using the same technique, fields angles and treatment planning system of the original ones. The pattern of recurrence was in field, marginal and distant in 88, 10 and 2 % respectively and was similar in in silico plans. The margin reduction appears to spare 100 cc of healthy brain by 57 Gy-volume (p = 0.02). The target coverage was worse in standard plans (pt student < 0.001), especially if the tumour was near to organs at risk (pχ2 < 0.001). PTV coverage was better with IMRT and helical-IMRT, than conformal-3D (pAnova test = 0.038). This difference was no more significant with in silico planning. A higher incidence of asthenia and leuko-encephalopathy was observed in patients with greater percentage of healthy brain included in 57 Gy-volume. No differences in the pattern of recurrence according to margins were found. The margin reduction determines sparing of healthy brain and could possibly reduce the incidence of late toxicity. Margin reduction could allow to use less sophisticated techniques, ensuring appropriate target coverage, and the choice of more costly techniques could be reserved to selected cases.
Subject(s)
Brain Neoplasms/diagnostic imaging , Brain Neoplasms/therapy , Chemoradiotherapy , Glioblastoma/diagnostic imaging , Glioblastoma/therapy , Radiotherapy, Conformal , Aged , Brain Neoplasms/epidemiology , Chemoradiotherapy/adverse effects , Female , Glioblastoma/epidemiology , Humans , Incidence , Male , Middle Aged , Neoplasm Recurrence, Local/diagnostic imaging , Organs at Risk , Radiotherapy, Conformal/adverse effects , Recurrence , Retrospective Studies , Treatment Outcome , Tumor BurdenABSTRACT
AIMS AND BACKGROUND: Radiotherapy is the standard treatment of glioblastoma. Three-dimensional conformal radiotherapy is the standard technique to treat glioblastoma. Intensity-modulated radiotherapy and helical intensity-modulated radiotherapy (tomotherapy) are becoming widely used. The present study compared three-dimensional conformal radiotherapy, intensity-modulated radiotherapy and tomotherapy in terms of target coverage and preservation of organs at risk. METHODS: Ten patients treated with three-dimensional conformal radiotherapy, with a target volume close to or superimposed to the organs at risk, were retrospectively selected. The plans were re-planned with step-and-shoot 3/5 fields intensity-modulated radiotherapy and tomotherapy. Target coverage and sparing of organs at risk were statistically compared. RESULTS: Mean planning target volume V95% improved with sophisticated techniques (87.2%, 93.2%, 97.6% with three-dimensional conformal radiotherapy, intensity-modulated radiotherapy and tomotherapy, respectively). The comparison of three-dimensional conformal radiotherapy and intensity-modulated radiotherapy did not show significant differences, whereas differences were significant when three-dimensional conformal radiotherapy and tomotherapy as well as intensity-modulated radiotherapy and tomotherapy were compared. Mean planning target volume/clinical target volume D99-D98-D95 were not different between three-dimensional conformal radiotherapy and intensity-modulated radiotherapy, but they were different between tomotherapy and three-dimensional conformal radiotherapy and intensity-modulated radiotherapy, with better clinical target volume/and planning target volume coverage with the tomotherapy plans. Brain D33/66 were 31.1/11.8 Gy, 37.5/18.3 Gy and 28.5/14.7 Gy with three-dimensional conformal radiotherapy, intensity-modulated radiotherapy and tomotherapy, respectively. Mean brainstem, optic nerves and chiasma Dmax were always within the defined constraints. The homogeneity index improved with intensity-modulated radiotherapy/tomotherapy compared to three-dimensional conformal radiotherapy. Tomotherapy was better than intensity-modulated radiotherapy in all patients. CONCLUSIONS: In this selected group of patients, a significant dosimetric advantage was evident for tomotherapy compared with three-dimensional conformal radiotherapy and intensity-modulated radiotherapy. Significant advantages were evident in terms of panning target volume coverage (V95), D99, D98 and D95. The clinical significance of the results should be defined.
