A phase I dose escalation study using simultaneous integrated-boost IMRT with temozolomide in patients with unifocal glioblastoma

[Radiation dose intensification for glioblastoma]

Glioblastoma is the most common brain tumor in adults; its treatment includes surgical excision or biopsy followed by radio-chemotherapy. Even if radiotherapy increases the survival of all patients regardless of their age or their general condition, there are always sources of radioresistance, where relapses occur and therefore treatment fails. Indeed, these foci result in a local relapse, which is observed in 95% of cases in the irradiation fields. We will describe here the current approaches to overcome this radioresistance by dose escalation, without or with guidance by metabolic and functional imaging (dose-painting). We will detail several prospective trials including the French phase III trial, SPECTRO-GLIO, randomizing the use of an integrated boost guided by spectrometric magnetic resonance imaging and similar trials developed across the Atlantic. We will also discuss approaches using different PET markers as well as diffusion or perfusion magnetic resonance imaging.

Post-Operative Accelerated-Hypofractionated Chemoradiation With Volumetric Modulated Arc Therapy and Simultaneous Integrated Boost in Glioblastoma: A Phase I Study (ISIDE-BT-2)

Background

Glioblastoma Multiforme (GBM) is the most common primary brain cancer and one of the most lethal tumors. Theoretically, modern radiotherapy (RT) techniques allow dose-escalation due to the reduced irradiation of healthy tissues. This study aimed to define the adjuvant maximum tolerated dose (MTD) using volumetric modulated arc RT with simultaneous integrated boost (VMAT-SIB) plus standard dose temozolomide (TMZ) in GBM.

Methods

A Phase I clinical trial was performed in operated GBM patients using VMAT-SIB technique with progressively increased total dose. RT was delivered in 25 fractions (5 weeks) to two planning target volumes (PTVs) defined by adding a 5-mm margin to the clinical target volumes (CTVs). The CTV₁ was the tumor bed plus the MRI enhancing residual lesion with 10-mm margin. The CTV₂ was the CTV₁ plus 20-mm margin. Only PTV₁ dose was escalated (planned dose levels: 72.5, 75, 77.5, 80, 82.5, 85 Gy), while PTV₂ dose remained unchanged (45 Gy/1.8 Gy). Concurrent and sequential TMZ was prescribed according to the EORTC/NCIC protocol. Dose-limiting toxicities (DLTs) were defined as any G ≥ 3 non-hematological acute toxicity or any G ≥ 4 acute hematological toxicities (RTOG scale) or any G ≥ 2 late toxicities (RTOG-EORTC scale).

Results

Thirty-seven patients (M/F: 21/16; median age: 59 years; median follow-up: 12 months) were enrolled and treated as follows: 6 patients (72.5 Gy), 10 patients (75 Gy), 10 patients (77.5 Gy), 9 patients (80 Gy), 2 patients (82.5 Gy), and 0 patients (85 Gy). Eleven patients (29.7%) had G1-2 acute neurological toxicity, while 3 patients (8.1%) showed G ≥ 3 acute neurological toxicities at 77.5 Gy, 80 Gy, and 82.5 Gy levels, respectively. Since two DLTs (G3 neurological: 1 patient and G5 hematological toxicity: 1 patient) were observed at 82.5 Gy level, the trial was closed and the 80 Gy dose-level was defined as the MTD. Two asymptomatic histologically proven radionecrosis were recorded.

Conclusions

According to the results of this Phase I trial, 80 Gy in 25 fractions accelerated hypofractionated RT is the MTD using VMAT-SIB plus standard dose TMZ in resected GBM.

Retrospective comparison of standard and escalated doses of radiotherapy in newly diagnosed glioblastoma patients treated with concurrent and adjuvant temozolomide

BACKGROUND

To compare the efficacies of standard dose-(SDRT) and escalated dose radiotherapy (EDRT) in newly diagnosed glioblastoma (GBM) with concurrent and adjuvant temozolomide (TMZ).

MATERIALS AND METHODS

Outcomes of 126 newly diagnosed GBM patients who received SDRT (60 Gy, 30 fractions) or EDRT (70 Gy, 30 fractions) with concurrent plus adjuvant TMZ were retrospectively analyzed. Both groups received concurrent TMZ (75 mg/m²) during the course of RT and at least one course of adjuvant TMZ (150-200 mg/m²), thereafter. Overall survival (OS) and local progression free survival (LPFS) constituted the primary and secondary endpoints, respectively.

RESULTS

At median 14.2 months follow-up, 26 (20.6%) patients were alive. Median LPFS and OS were 9.2 [95% confidence interval (CI); 8.4-10.0] and 15.4 months (95% CI; 12.1-18.8), respectively, for the entire cohort. Although the median OS was numerically superior in the EDRT this difference could not reach statistical significance (22.0 vs. 14.9 months; P = 0.45), Likewise, LPFS was also (9.9 vs. 8.9 months; P = 0.89) not different between the two treatment groups. In multivariate analysis, better recursive partitioning analysis class (3-4 vs. 5; P = 0.044) and extensive surgery (gross total resection vs. subtotal resection/biopsy only; P= 0.021) were identified to associate significantly with superior OS times, irrespective of the RT protocol.

CONCLUSIONS

Although the current median OS of 22 months of the EDRT group is promising, no statistically significant survival advantage for EDRT was observed even in the presence of TMZ. Randomized studies with larger population sizes and available genetic markers are warranted to conclude more reliably on the fate of EDRT plus TMZ.

18F-FDOPA PET/CT Combined with MRI for Gross Tumor Volume Delineation in Patients with Skull Base Paraganglioma

In this simulation study, we assessed differences in gross tumor volume (GTV) in a series of skull base paragangliomas (SBPGLs) using magnetic resonance imaging (MRI), ¹⁸F-dihydroxyphenylalanine (¹⁸F-FDOPA) combined positron emission tomography/computed tomography (PET/CT), and ¹⁸F-FDOPA PET/MRI images obtained by rigid alignment of PET and MRI. GTV was delineated in 16 patients with SBPGLs on MRI (GTV_MRI), ¹⁸F-FDOPA PET/CT (GTV_PET), and combined PET/MRI (GTV_PET/MRI). GTV_PET/MRI was the union of GTV_MRI and GTV_PET after visual adjustment. Three observers delineated GTV_MRI and GTV_PET/MRI independently. Excellent interobserver reproducibility was found for both GTV_MRI and GTV_PET/MRI. GTV_PET and GTV_MRI were not significantly different. However, there was some spatial difference between the locations of GTV_MRI, GTV_PET, and GTV_PET/MRI. The Dice similarity coefficient median value was 0.4 between PET/CT and MRI, and 0.8 between MRI and PET/MRI. The combined use of PET/MRI produced a larger GTV than MRI alone. Nevertheless, both the target-delivered dose and organs-at-risk conservancy were respected when treatment was planned on the PET/MRI-matched data set. Future integration of ¹⁸F-FDOPA PET/CT into clinical practice will be necessary to evaluate the influence of this diagnostic modality on SBPGL therapeutic management. If the clinical utility of ¹⁸F-FDOPA PET/CT and/or PET/MRI is confirmed, GTV_PET/MRI should be considered for tailored radiotherapy planning in patients with SBPGL.

Molecular PET imaging in adaptive radiotherapy: brain

INTRODUCTION

Owing to their heterogeneity and radioresistance, the prognosis of primitive brain tumors, which are mainly glial tumors, remains poor. Dose escalation in radioresistant areas is a potential issue for improving local control and overall survival. This review focuses on advances in biological and metabolic imaging of brain tumors that are proving to be essential for defining tumor target volumes in radiation therapy (RT) and for increasing the use of DPRT (dose painting RT) and ART (adaptative RT), to optimize dose in radio-resistant areas.

EVIDENCE ACQUISITION

Various biological imaging modalities such as PET (hypoxia, glucidic metabolism, protidic metabolism, cellular proliferation, inflammation, cellular membrane synthesis) and MRI (spectroscopy) may be used to identify these areas of radioresistance. The integration of these biological imaging modalities improves the diagnosis, prognosis and treatment of brain tumors.

EVIDENCE SYNTHESIS

Technological improvements (PET and MRI), the development of research, and intensive cooperation between different departments are necessary before using daily metabolic imaging (PET and MRI) to treat patients with brain tumors.

CONCLUSIONS

The adaptation of treatment volumes during RT (ART) seems promising, but its development requires improvements in several areas and an interdisciplinary approach involving radiology, nuclear medicine and radiotherapy. We review the literature on biological imaging to outline the perspectives for using DPRT and ART in brain tumors.

Clinical and dosimetric study of radiotherapy for glioblastoma: three-dimensional conformal radiotherapy versus intensity-modulated radiotherapy

BACKGROUND AND PURPOSE

We aimed to compare three-dimensional conformal radiotherapy (3D-CRT) with intensity-modulated radiotherapy (IMRT) for the treatment of glioblastoma.

MATERIALS AND METHODS

Retrospective study of 220 patients with glioblastoma, treated with 3D-CRT or IMRT, with or without surgery. Dosimetric parameters as well as clinical and survival data for the two techniques were analyzed and compared.

RESULTS

The median conformity index was 1.53 (range 0-2.69) for 3D-CRT and 1.25 (range 0.97-2.01) for IMRT, p < 10^-4. The median homogeneity index was 0.10 (range 0.03-0.32) for 3D-CRT and 0.07 (range 0.03-0.18) for IMRT, p < 10^-4. There were significantly fewer acute grade 1 and 2 neurological toxicities in the IMRT group especially for edema (1.3 versus 12.4%, p = 0.017), concentration disorders (6.6 versus 19.9%, p = 0.003) and consciousness disorders (2.6 versus 13.2%, p = 0.002) although IMRT patients had a significantly worse pre-treatment neurological status than 3D-CRT patients. Median survival was 16.0 months (range 11.9-17.8) for IMRT and 13.4 months (range 11.7-15.7) for 3D-CRT patients (p = 0.542).

CONCLUSION

IMRT improved target conformity and reduced neurological toxicities for patients with glioblastomas.

The extent of edema and tumor synchronous invasion into the subventricular zone and corpus callosum classify outcomes and radiotherapy strategies of glioblastomas

BACKGROUND AND PURPOSE

Irradiating glioblastoma preoperative edema (PE) remains controversial. We investigated the associations between tumors' PE extent with invasion into synchronous subventricular zone and corpus callosum (sSVZCC) and treatment outcomes to provide the clinical evidence for radiotherapy decision-making.

MATERIAL AND METHODS

Extensive PE (EPE) was defined as PE extending ≥2 cm from the tumor edge and extensive progressive disease (EPD) as tumors spreading ≥2 cm from the preoperative tumor edge along PE. The survival and progression patterns were analyzed according to EPE and sSVZCC invasion.

RESULTS

In total, 136 patients were followed for a median of 74.9 (range, 47.6-102.1) months. The median overall survival and progression-free survival were 19.7 versus 28.6 months (p = 0.005) and 11.0 versus 17.4 months (p = 0.011) in patients with EPE+ versus EPE-, and were 18.7 versus 25.4 months (p = 0.021) and 10.7 versus 14.6 months (p = 0.020) in those with sSVZCC+ versus sSVZCC-. The EPD rates for tumors with EPE-/sSVZCC-, EPE-/sSVZCC+, EPE+/sSVZCC-, and EPE+/sSVZCC+ were 2.8%, 7.1%, 37.0%, and 71.9%, respectively. In EPE+/sSVZCC+, tumor migration was associated with the PE extending along the corpus callosum (77.8%) and subventricular zone (50.0%).

CONCLUSIONS

Our results support the need for developing individualized irradiation strategies for glioblastomas according to EPE and sSVZCC.