IMRT or 3D-CRT in Glioblastoma? A Dosimetric Criterion for Patient Selection

Abstract

Intensity modulated radiation therapy (IMRT) is increasingly employed in glioblastoma (GBM) treatment. The present work aimed to assess which clinical-dosimetric scenario could benefit the most from IMRT application, with respect to three-dimensional conformal radiation therapy (3D-CRT). The number of organs at risk (OARs) overlapping the planning target volume (PTV) was the parameter describing the clinical-dosimetric pattern. Based on the results, a dosimetric decision criterion to select the most appropriate treatment technique is provided. Seventeen previously irradiated patients were retrieved and re-planned with both 3D-CRT and IMRT. The prescribed dose was 60 Gy/30fx. The cases were divided into 4 groups (4 patients in each group). Each group represents the scenario where 0, 1, 2 or 3 OARs overlapped the target volume, respectively. Furthermore, in one case, 4 OARs overlapped the PTV. The techniques were compared also in terms of irradiated healthy brain tissue. The results were evaluated by paired t-test. IMRT always provided better target coverage (V95%) than 3D-CRT, regardless the clinical-dosimetric scenario: difference ranged from 0.82% (p = 0.4) for scenario 0 to 7.8% (p = 0.02) for scenario 3, passing through 2.54% (p = 0.18) and 5.93% (p = 0.08) for scenario 1 and 2, respectively. IMRT and 3D-CRT achieved comparable results in terms of dose homogeneity and conformity. Concerning the irradiation of serial-kind OARs, both techniques provided nearly identical results. A statistically significant dose reduction to the healthy brain in favor of IMRT was scored. IMRT seems a superior technique compared to 3D-CRT when there are multiple overlaps between OAR and PTV. In this scenario, IMRT allows for a better target coverage while maintaining equivalent OARs sparing and reducing healthy brain irradiation. The results from our patients dataset suggests that the overlap of three OARs can be used as a dosimetric criterion to select which patients should receive IMRT treatment.

Survival improvements with adjuvant therapy in patients with glioblastoma

“…In the current series, the resection rate over the cohort years was 46% (2007–2008), 54% (2009–2010), 34% , 56% , suggestive of a similar trend over time. Although there is no randomized data comparing IMRT to 3D conformal radiotherapy, this technique has been shown to improve dose conformity as well as reducing high doses to the normal sensitive surrounding structures . Some studies have been able to achieve high dose conformity and target coverage while still limiting the low dose wash to the brain .…”

“…The near total resection rate in the 2003 EORTC‐NCIC study was 39%, while in the subsequent 2010 European‐based trial investigating a targeted drug cilengitide it was 44% . In the current series, the resection rate over the cohort years was 46% (2007–2008), 54% (2009–2010), 34% , 56% , suggestive of a similar trend over time. Although there is no randomized data comparing IMRT to 3D conformal radiotherapy, this technique has been shown to improve dose conformity as well as reducing high doses to the normal sensitive surrounding structures .…”

“…Although there is no randomized data comparing IMRT to 3D conformal radiotherapy, this technique has been shown to improve dose conformity as well as reducing high doses to the normal sensitive surrounding structures. 14,15 Some studies have been able to achieve high dose conformity and target coverage while still limiting the low dose wash to the brain. 16 Ideally, these findings need to be correlated with long-term outcome data comparing outcomes and toxicity.…”

An Integrated Widefield Imaging and Spectroscopy System for Contrast-Enhanced, Image-Guided Resection of Tumors

“…Here, we report the design and initial pre-clinical testing of an intraoperative imaging system that uses a handheld probe for simultaneous excitation and spectroscopic detection of NIR fluorescent contrast agents in combination with a widefield video-rate camera system for intuitive visualization. Optical imaging systems based on detecting contrast-enhanced fluorescence emission have been developed, including point imaging and widefield imaging systems [13–18]; we present an improvement over the current state of the art by incorporating aspects of both systems for optimized intraoperative tumor detection.…”

Imaging Surrogates of Infiltration Obtained Via Multiparametric Imaging Pattern Analysis Predict Subsequent Location of Recurrence of Glioblastoma

“…2–4 Advanced imaging modalities have improved the precision of radiotherapy through enhanced tumor delineation, whereas conformal radiotherapy and intensity-modulated radiation therapy (IMRT) allow for an increased radiation dose to the tumor bed and surrounding margin while preserving critical brain structures. 5,6 …”