Early changes in glioblastoma metabolism measured by MR spectroscopic imaging during combination of anti-angiogenic cediranib and chemoradiation therapy are associated with survival

Precise assessment of treatment response in glioblastoma during combined anti-angiogenic and chemoradiation remains a challenge. In particular, early detection of treatment response by standard anatomical imaging is confounded by pseudo-response or pseudo-progression. Metabolic changes may be more specific for tumor physiology and less confounded by changes in blood-brain barrier permeability. We hypothesize that metabolic changes probed by magnetic resonance spectroscopic imaging can stratify patient response early during combination therapy. We performed a prospective longitudinal imaging study in newly diagnosed glioblastoma patients enrolled in a phase II clinical trial of the pan-vascular endothelial growth factor receptor inhibitor cediranib in combination with standard fractionated radiation and temozolomide (chemoradiation). Forty patients were imaged weekly during therapy with an imaging protocol that included magnetic resonance spectroscopic imaging, perfusion magnetic resonance imaging, and anatomical magnetic resonance imaging. Data were analyzed using receiver operator characteristics, Cox proportional hazards model, and Kaplan-Meier survival plots. We observed that the ratio of total choline to healthy creatine after 1 month of treatment was significantly associated with overall survival, and provided as single parameter: (1) the largest area under curve (0.859) in receiver operator characteristics, (2) the highest hazard ratio (HR = 85.85, P = 0.006) in Cox proportional hazards model, (3) the largest separation (P = 0.004) in Kaplan-Meier survival plots. An inverse correlation was observed between total choline/healthy creatine and cerebral blood flow, but no significant relation to tumor volumetrics was identified. Our results suggest that in vivo metabolic biomarkers obtained by magnetic resonance spectroscopic imaging may be an early indicator of response to anti-angiogenic therapy combined with standard chemoradiation in newly diagnosed glioblastoma.

ACRIN 6684 assessment of tumor hypoxia in glioblastoma using 18F-fluoromisonidazole with PET and MRI

TPS10635

Background: Glioblastoma (GBM) is an aggressive type of primary malignant brain tumor and despite treatment with surgery, radiation, and temozolomide (TMZ) chemotherapy, median overall survival (OS) remains poor. A pathologic hallmark of GBM is tumor necrosis, a suspected result from endogenous tumor hypoxia. Angiogenesis is stimulated by hypoxia-driven signaling cascades and is required for tumor proliferation. The inefficient blood supply of these hypoxic tumors also limits the efficacy of chemotherapy and radiotherapy. Surviving hypoxic tumor cells may be selected out and proliferate as a more aggressive tumor subtype, therefore hindering OS. 18F-Fluoromisonidazole (FMISO) is a PET radiotracer whose uptake in hypoxic tissues can be measured radiographically. The degree of tumor hypoxia has been negatively associated with time to tumor progression and survival (Spence et al, 2008). Knowledge of the degree/distribution of tumor hypoxia by PET uptake and perfusion MRI parameters may provide prognostic information and help guide therapy for patients with GBM. Methods: In this phase II prospective single arm multi-institution study, patients will undergo baseline FMISO PET and MR imaging two weeks prior to chemoradiotherapy (CRT). A subset of patients will receive a second FMISO PET one week prior to CRT to assess reproducibility. Clinical outcomes of OS and 6-month progression-free survival (PFS-6) will be correlated to PET and MRI parameters. Eligibility: Pathologically confirmed GBM with residual tumor after surgery (including T2/FLAIR hyperintensity consistent with tumor) scheduled to receive standard fractionated radiation therapy and temozolomide alone or with an anti-VEGF agent or PARP inhibitor. Current enrollment: 22 patients of 50 sample size Contact information: Please contact the PI, Elizabeth R. Gerstner, MD ( egerstner@partners.org ) for additional information. Significance: With a better understanding of the extent of tumor hypoxia and changes in hypoxia levels from treatment, more effective therapies could be developed to inhibit GBM growth, target hypoxic areas and individualize patient care.

Normal diffusion-weighted MRI during stroke-like deficits

BACKGROUND

Diffusion-weighted MRI (DWI) represents a major advance in the early diagnosis of acute ischemic stroke. When abnormal in patients with stroke-like deficit, DWI usually establishes the presence and location of ischemic brain injury. However, this is not always the case.

OBJECTIVE

To investigate patients with stroke-like deficits occurring without DWI abnormalities in brain regions clinically suspected to be responsible.

METHODS

We identified 27 of 782 consecutive patients scanned when stroke-like neurologic deficits were still present and who had normal DWI in the brain region(s) clinically implicated. Based on all the clinical and radiologic data, we attempted to arrive at a pathophysiologic diagnosis in each.

RESULTS

Best final diagnosis was a stroke mimic in 37% and a cerebral ischemic event in 63%. Stroke mimics (10 patients) included migraine, seizures, functional disorder, transient global amnesia, and brain tumor. The remaining patients were considered to have had cerebral ischemic events: lacunar syndrome (7 patients; 3 with infarcts demonstrated subsequently) and hemispheric cortical syndrome (10 patients; 5 with TIA, 2 with prolonged reversible deficits, 3 with infarction on follow-up imaging). In each of the latter three patients, the regions destined to infarct showed decreased perfusion on the initial hemodynamically weighted MRI (HWI).

CONCLUSIONS

Normal DWI in patients with stroke-like deficits should stimulate a search for nonischemic cause of symptoms. However, more than one-half of such patients have an ischemic cause as the best clinical diagnosis. Small brainstem lacunar infarctions may escape detection. Concomitant HWI can identify some patients with brain ischemia that is symptomatic but not yet to the stage of causing DWI abnormality.