Magnetic resonance spectroscopy in cancer research

Magnetic resonance spectroscopy (MRS), a useful complement to magnetic resonance imaging (MRI), yields a wealth of information about the biochemical content of tissue and the dynamic behavior of its component molecules. When used for colonic tumors, it can distinguish between those with and those without metastatic potential, through the relaxation time (T2) of the resonance at 1.3 ppm in the proton (1H) MRS spectrum. The presence of peaks near 3.2 ppm correlates well with tumor stage and allows identification of premalignant tissue. Two-dimensional MRS provides an independent method for staging colonic tumors by means of a crosspeak between 1.3 and 4.2 ppm. With a combination of MRS and MRI (localized spectroscopy) it should soon be possible to locate and stage a colonic tumor without physical intervention. In the plasma of patients who have cancer there often exists a lipoprotein band with MRS characteristics similar to those of colonic tumors. It also occurs occasionally in healthy persons and in those who have diseases other than cancer. The lipoprotein appears to be lipoprotein (a), which also has been associated with cardiac disease. We have used a simple MRS measurement on unfractionated plasma, which has been suggested as a reliable indicator of the presence of cancer, on approximately 1800 persons who were healthy, ill with cancer, and ill with other diseases. We found it unsatisfactory as a screening method for an asymptomatic population, because essentially it measures the plasma triglyceride level, especially that in very low-density lipoprotein, which can be elevated for a variety of reasons unrelated to cancer.