[CANCER RESEARCH 56. 2964-2972. July I. 1996] Metabolic Characterization of Human Soft Tissue Sarcomas in Vivo and in Vitro Using Proton-decoupled Phosphorus Magnetic Resonance Spectroscopy1 Chun-Wei Li, Annette C. Kuesel, Kristin A. Padavic-Shaller, Joseph Murphy-Boesch, Burton L. Eisenberg, Richard G. Schmidt, Reinhard W. von Roemeling, Arthur S. Patchefsky, Truman R. Brown, and William G. Negendank2 Departments of Nuclear Magnetic Résonanceand Medical Spectroscopy ¡C-W.L. A. C. K.. K. A. P-S.. J. M-B., T. R. B.. W. G. N.J. Surgical Oncology ¡B.L E.. R. G. SJ. Medical Oncology ¡R.W. V. R.¡.ami Pathology ¡A.S. P.], Fox Chase Cancer Center. Philadelphia. Pennsylvania Will ABSTRACT We applied 'H-decoupling and nuclear Overhauser enhancement to obtain well-resolved "I' magnetic resonance spectra accurately localized to 20 soft tissue sarcomas in vivo, using three-dimensional chemical shift imaging. Fifteen spectra had large phosphomonoester signals (21% of total phosphorus) that contained high amounts of phosphoethanolamine (compared to those of phosphocholine) but no signals from glycerophos- phoethanolamine, and glycerophosphocholine was detected in only four cases. Prominent nucleoside triphosphates (52% of phosphorus) and low inorganic phosphate (10% of phosphorus) indicated that a large fraction of these 15 sarcomas contained viable cells, and this impression was confirmed histologically in 13 of the sarcomas. High-resolution in vitro "I' spectra of extracts of surgical specimens of four of the sarcomas studied in vivo and six additional sarcomas confirmed the in vivo assignments of metabolites and revealed considerable inter- and intratumoral variations of metabolite concentrations associated with histológica) variations in the relative amounts of cells and of matrix materials or spontaneous necrosis. Seven sarcomas, all high grade with pleomorphic or round cells rather than spindle cells, contained an unidentified phosphodiester signal in vivn; its absence in the extract spectra indicates that it may be from an abnor mally mobile membrane component. We have documented a means to obtain new information about in vivo metabolism in human sarcomas and to provide a basis on which to examine the uses ol "I1 magnetic resonance spectroscopy in the clinical management of sarcomas. INTRODUCTION Observations that indicate the importance of aspects of energy metabolism and phospholipid metabolism in malignant behavior, treatment sensitivity, and resistance both in experimental models (1. 2) and in patients (3-7) have stimulated interest in the biochemistry of sarcomas. An attractive way to obtain information about the metab olism of sarcomas in vivo is to use 31P MRS3. The 3IP MR spectrum has signals from phospholipid metabolites, NTPs. and other energy- related metabolites, and it provides a means to measure intracellular pH. The "P MR spectra of approximately 100 human soft tissue sarcomas in vivo have been reported (1, 3-6, 8-16). In general, these spectra had relatively strong signal intensities in the PME and PDE regions and an intracellular pH (determined from the position of the P¡ signal on the frequency axis) of approximately 7.25. However, most of the reported spectra were incompletely localized to the sarcomas: (a) many were heavily contaminated with signals from muscle; (b) Received 4/17/96: aecepled 4/24/96. The cosls of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported by NIH Grants CA56960. CA54339. and CA41078 and by Siemens Medical Systems (Iselin, NJ). 2 To whom requests for reprints should be addressed, at Department of Nuclear Magnetic Resonance and Medical Spectroscopy, Fox Chase Cancer Center, 7701 Burholme Avenue. Philadelphia. PA 19111 ' The abbreviations used are: MRS. magnetic resonance spectroscopy: NMR, nuclear magnetic resonance; MRI. magnetic resonance imaging: PME. phosphomonoester: PDE. phosphodiester; NTP. nucleoside triphosphate: PCr. phosphocreatine; PEth. phosphoeth anolamine: PChol. phosphocholine: GPEth. glycerophosphoethanolamine; GPChol. glyc erophosphocholine; NOE. nuclear Overhauser effect: CSI. chemical shift imaging: NDP. nucleoside diphosphate; MR. magnetic resonance: RIF-1. radiation-induced fibrosarcoma. many had insufficient resolution to clearly distinguish overlapping PME. P¡, and PDE signals: and (c) none had sufficient resolution to distinguish the major components within the PME and PDE regions. Two factors contribute to the poor resolution of metabolites in the 3'P MR spectra: (a) the inhomogeneity of the magnetic field within the region of interest. The adequacy of magnetic field homogeneity depends upon the extent of the efforts devoted to shimming proce dures: and (b) the broadening of the 31P signal peaks by coupling between magnetic fields of 3'P nuclei and those of neighboring 'H. This effect may be reduced by radio frequency irradiation of 'H during the acquisition of 3'P signals, a technique referred to as 'H-decoupling. In addition, the irradiation of 'H between acquisitions can increase some of the 3IP signal intensities by a process called NOE enhancement. We have recently applied the combination of 'H-decoupling and full NOE enhancement in vivo to 3IP MRS studies of brain, calf muscle, liver, and non-Hodgkin's lymphomas (17-20). We report here the use of this technique, in conjunction with the means to optimize the magnetic field homogeneity automatically within the region of interest (autoshimming; Ref. 21) to improve the resolution within the PME and PDE regions of the spectrum in patients with sarcomas. We used MRI-directed, three-dimensional CSI to accurately localize 31P MR spectra to the regions of interest (22). To permit application of these techniques in various anatomic sites, we constructed dual-tuned (3IP and 'H) surface coil arrangements. This approach enabled us to obtain more information about the in vivo metabolic characteristics of soft tissue sarcomas than has heretofore been available. Soft tissue sarcomas are heterogeneous histologically. Many con tain large amounts of matrix materials of a fibroid, lipoid. or myxoid character, and many undergo spontaneous focal necrosis. These fac tors can reduce the fraction of viable cells within a region studied by MRS and therefore reduce the metabolite signals relative to the noise in the spectrum. This could account in part for the considerable variations in quality reported among in vivo 3IP spectra in human sarcomas (1, 3-6, 8-16). To examine this issue, we determined the histopathological characteristics of the sarcomas that were studied in vivo before surgery, and we obtained high-field "P MR spectra of the water-soluble extracts of surgical specimens of soft tissue sarcomas, some of which were also studied in vivo. This approach enabled us to confirm the in vivo assignments of metabolites to observed signals, to obtain molar concentrations of the metabolites, and to examine the aspects of inter- and intratumoral heterogeneity. PATIENTS AND METHODS Patient Population. Eligibility for the in vivo 3IP MRS study required a biopsy-proven diagnosis of soft-tissue sarcoma, a tumor mass ot approximately 3-cm diameter or larger located within 10 cm of the surface of the body, an absence of the standard contraindications to MRI. and signed informed consent as approved by the Institutional Review Board. Of 20 patients. 16 were newly diagnosed. 3 were recurrent after prior treatment, and 1 was resistant to chemotherapy. From four of these patients and six additional patients, portions of surgical specimens were obtained and extracted for in vitro "P MRS study. 2964 on June 24, 2015. © 1996 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from