MAGMA (1994) 2, 253-257 MRS studies of cancer J.R. Griffiths,* R.J. Maxwell, 1 S.L. Howells, F.A. Howe, 1 S.P. Robinson, 1 M. Stubbs, ~ C.L McCoy, 1 L.M. Rodrigues, 1 C.L. Parkins 2 and D.J. Chaplin 2 1CRC Biomedical Magnetic Resonance Research Group, St. George's Hospital Medical School, London, SW17 ORE, UK 2CRC Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex HA6 2RN, UK Cancer was an obvious disease to study by magnetic resonance spectroscopy (MRS); it produces large lesions that give clearly abnormal spectra, all treatment methods leave much to be desired, and radiotherapy, in particular, is limited by tissue hypoxia, a process that can be investigated by MRS. 31p MRS has shown that tumor cells are not acidic, as had been thought; instead, the pH gradient across the tumor cell membrane is the reverse of that in a normal cell. This change in hydrogen-ion gradient is accompanied by changes in gradients of many other ions. Tumor oxygenation can be monitored in animal tumor models using the techniques employed for functional magnetic resonance imaging (MRI) of the brain. Large changes in signal are observed when drugs that reduce tumor blood flow are administered. tH NMR spectra of acid extracts of tumor or normal tissue biopsies contain sufficient information to permit classification (and thus, perhaps, diagnosis) if computer-based pattern recognition techniques are employed. Surprisingly, the same technique gives quite good classification of 31p spectra taken in vivo. Can MRS be applied in cancer therapy? Studies on tumor ion balance will help in the design of anticancer drugs and other therapies. Tumor blood flow studies using MRI could be applied to individual patients to predict the usefulness of radiotherapy and to assist in radiotherapy planning. Pattern recognition methods could automate the screening of biopsies and could also assist in interpretation of human spectra taken in vivo. Keywords: Magnetic resonance spectroscopy, tumors, ion balance, functional MRI, blood flow, pattern recognition. INTRODUCTION The use of magnetic resonance spectroscopy (MRS) to study cancer in vivo was a relatively late development compared with heart, muscle, and other body tissues, although in retrospect it was an obvious choice. Cancer is a common disease, and tumors contain abnormal concentrations of some metabolites. Many are several centimeters in diameter before they are detected, and a reasonable number are found in locations in which they can give adequate MRS signals with current techniques. Furthermore, there is an *Address for correspondence: CRC Biomedical Magnetic Reso- nance Research Group, St. George's Hospital Medical School, London SW17 ORE, UK. urgent need to improve the efficacy of cancer therapy. Nonsurgical anticancer therapies such as radio- therapy, chemotherapy, and endocrine therapy are all of limited use against the major solid tumors. The same is true of the newer therapies, including hyper- thermia, photodynamic therapy, immunotherapy, and those based on biological response modifiers (e.g., tumor necrosis factor or interferon). Using noninva- sive measurements of tumor chemistry, we should be able to improve our understanding of these therapies and, perhaps, to monitor and thus optimize the treatment of individual patients. So far, however, the major successes of MRS in cancer have been con- cerned with research. As with many other diseases, we have learned much about the physiology and biochem- istry of cancer from MRS, but we have not yet been able to apply it routinely in the clinic. 0968-5243 © 1994 Chapman & Hall