Diffusely Infiltrating Gliomas with Non-Significant Contrast-Enhancement: Is 1 H-Magnetic Resonance Spectroscopy Chemical Shift Imaging a Clinically Reliable Technique for Detection of Malignant Intratumoral Areas Department of Neurosurgery Georg Widhalm

Inhomogeneity of Gliomas Diffusely infiltrating gliomas (DIG) are frequently histologically heterogeneous with development of malignant intratumoral areas (=anaplastic foci) Surgery: Problem of target definition (=representative tumor sample) for intraoperative tissue sampling Neuropathology: Danger of histopathological undergrading Adjuvant treatment: Accurate histological dignosis is essential for allocation of the patients to the adequate treatment Optimization of intraoperative tumor tissue sampling is needed Paulus et al; Cancer; 1989

Current Methods for Detection of Anaplastic Foci MRI Routinely, anaplastic foci are identified by contrast- enhancement (CE) on MRI sampled intraoperatively using neuronavigational guidance However, a considerable number of DIG WHO grade II and III lack significant CE Therefore, CE is often not a reliable parameter for identification of anaplastic foci

DIG with non-significant CE Up to 55% of cases with non- significant CE are already WHO grade III gliomas DIG with non-significant CE constitute a special challenge to the neuroradiologist and neurosurgeon in selecting a representative intraoperative tumor ?

 Positron emission tomography (PET) is a powerful method for detection of anaplastic foci in DIG  Frequently PET with amino-acid tracers (e.g. ¹¹C-methionine-PET (MET-PET) or 18 F- fluoroethyl-L-tyrosine-PET (FET-PET) is used  Neuronavigation based on PET data co-registered with anatomic images is frequently used for intraoperative detection of malignant areas  However, PET is available only in highly specialized neurooncological centers Current Methods for Detection of Anaplastic Foci PET

In-plane multivoxel matrix (1 cm slice- thickness= 2-D CSI) Creation of color coded maps of metabolic ratios (Cho/NAA or Cho/Cr): red color code visualizes the tumor area with the highest CSI ratio New Methods for Detection of Anaplastic Foci 1 H-MR-Spectroscopy (MRS)

CSI sandwich (5 empty slices 5 identical CSI slices 5 empty slices) Step 2 Copy registration file = MR T1 CE (85 slices) MR T2 (15 slices) co-planar acquisition Step 1 Step 1 Image Fusion Step 3 Step 3 Load into Navigation System MR T1 CE + CSI on Navigation Screen Inegration of CSI into neuronavigation

Present study We investigated the clinical usability of CSI for detection of malignant areas in diffusely infiltrating gliomas in comparison to standard MET-PET 32 consecutive patients with diffusely infiltrating gliomas July 2007 and November 2009 MRI, 2-D CSI (3T MR scanner) and MET-PET in all patients CSI (Cho/Cr and Cho/NAA): ratio of > 1.0 was considered as pathologic MET-PET tumor/normal (T/N) brain ratio : normal (T/N: <1.15) unspecific tracer uptake (T/N: 1.15 and <1.5) pathologic (T/N: > 1.5 ) Histologic criteria of anaplasia as well as cell proliferation rate was assessed in tumor samples inside and outside of maximum pathologic PET and/or CSI ratios Widhalm et al; JNNP 2010

Study Design  Previous studies have shown that MET- PET max (maximal tracer uptake) represents areas with highest malignancy within diffusely infiltrating gliomas  Therefore we used in our study MET- PET max as reference for topographic correlation with CSI max (maximal pathologic CSI ratio) Sadeghi et al; AJNR; 2007

Study Design  After co-registration of MRI with CSI and MET-PET the topographic overlap of CSI max and PET max was analyzed: o overlap > 50% o overlap < 50% o distant (no overlap) PET max CSI max PET max + CSI max

Results MET-PET: 21/32 pathologic CSI: ratios abnormal in all patients

Topographic PET max /CSI max Correlation (n=21/32 pts) overlap > 50%: n= 18/21 pts overlap < 50%: n= 3/21 pts PET max CSI max PET max +CSI max

Topographic Cho/Cr max and Cho/NAA max Correlation (n=32 pts) Cho/Cr max Cho/NAA max Cho/NAA max +Cho/Cr max overlap > 50%: n= 24/32 pts overlap < 50%: n= 8/32 pts (6 central Cho/NAA, peripheral Cho/Cr)

Results-Neuropathology

CSI max, PET not pathologic CSI max, PET not pathologic (n=11/32; 7 WHO II, 4 WHO III tumors) MR T1 CE MET-PET negative CSI max HEMIB-1: > 42% mixed oligoastrocytoma WHO III HEMIB-1: < 9% inside CSI max outside CSI max

Limitations of Methods for iOP Identifikation of Anaplastic Foci Navigation with preoperative imaging: MRI+CE Metabolic imaging (PET, CSI) Cave: Brain shift! Intraoperative imaging: iOP MRI 5-ALA ? 5-ALA ?

5-Aminolevulinic acid (5-ALA) leads after oral application to intracellular accumulation of strongly fluorescing protophorphyrin IX in malignant glioma tissue Fluorescence can be visualised by a modified neurosurgical microscope with violet-blue excitation light Intraoperative identification of (residual)-malignant glioma tissue 5-ALA

17 gliomas with non-significant CE 3 T MRI +CM + MET-PET 5-ALA (20mg/kg KG ) 3 hours before anesthesia iOP: microscope was switched from conventional white light to violet-blue excitation light repeatedly 5-ALA fluorescence inside/outside PET max : yes (ALA+) or no (ALA-) was noted Topographic correlation with maximum PET tracer uptake (PET max ) 5-ALA in Gliomas with non-significant CE- 5-ALA is a Promising Marker for Detection of Anaplastic Foci in Diffusely Infiltrating Gliomas with Non-Significant CE Widhalm et al; Cancer 2010

5-ALA Fluorescence Focal 5-ALA fluorescence correlated topographically with PET max in all patients

MIB-1: ALA neg v/s ALA pos in the same tumor

PET max ALA + anaplastic focus Outside PET max ALA - low grade tumorMIB-1: 5% MIB-1: 14.4% Diagnosis: Anaplastic Astrocytoma WHO °III

Conclusions Detection of Anaplastic Foci in Gliomas with non-significant CE CSI is a clinically reliable technique for detection of malignant intratumoral areas within DIG with non- significant CE Intraoperative use of CSI by multimodal neuronavigation may increase the reliability of detection of malignant areas in glioma surgery and therefore optimize allocation of patients to adjuvant treatments 5-ALA is an additional promising marker in gliomas with non-significant CE for visualization of anaplastic foci that has the advantage of being unaffected from intraoperative brain-shift

Neurosurgery E. Knosp S. Wolfsberger G. Minchev A. Mert Radiology / High field-MRI D. Prayer M. Krssak G. Kasprian J. Furtner S. Trattnig E. Springer Institute of Neurology J. Hainfellner A. Wöhrer Neurology/Nuclear Medicine S. Asenbaum T. Traub-Weidinger Internal Medicine I C. Marosi M. Preusser Team approach 5-ALA training course Nov Vienna