Time-dependent effects of hormone-deprivation therapy on prostate metabolism as detected by combined magnetic resonance imaging and 3D magnetic resonance spectroscopic imaging

Combined MRI and 3D spectroscopic imaging (MR1/3D-MRSI) was used to study t he metabolic effects of hormone-deprivation therapy in 65 prostate cancer p atients, who underwent either short, intermediate, or long-term therapy, co mpared to 30 untreated control patients. There was a significant time-depen dent loss of the prostatic metabolites choline, creatine, citrate, and poly amines during hormone-deprivation therapy, resulting in the complete loss o f all observable metabolites (total metabolic atrophy) in 25% of patients o n long-term therapy. The amount and time-course of metabolite loss during t herapy significantly differed for healthy and malignant tissues. Citrate le vels decreased faster than choline and creatine levels during therapy, resu lting in an increase in the mean (choline + creatine)/citrate ratio with du ration of therapy. Due to a loss of all MRSI detectable citrate, this ratio could not be used to identify cancer in 69% of patients on long-term thera py. In the absence of citrate, however, residual prostate cancer could stil l be detected by elevated choline levels (choline/creatine ratio greater th an or equal to1.5), or the presence of only choline in the proton spectrum. The loss of citrate and the presence of total metabolic atrophy correlated roughly with decreasing serum prostatic specific antigen levels with incre asing therapy. In summary, MRI/3D-MRSI provided both a measure of residual cancer and a time-course of metabolic response following hormone-deprivatio n therapy. (C) 2001 Wiley-Liss, Inc.