31P MR spectroscopy in assessment of response to antiviral therapy for hepatitis C virus-related liver disease.

OBJECTIVE: An increase in the ratio of phosphomonoester (PME) to phosphodiester (PDE) during 31P MR spectroscopy of the liver has been observed with increasing severity of hepatitis C-related liver disease. The purpose of this study was to investigate the utility of 31P MR spectroscopy as a biomarker of response to interferon and ribavirin treatment.

SUBJECTS AND METHODS: Forty-seven patients with biopsy-proven hepatitis C undergoing viral eradication treatment with interferon and ribavirin underwent hepatic 31P MR spectroscopy at 1.5 T (voxel size, 70 x 70 x 70 mm; TR, 10,000; number of signals averaged, 48). All underwent baseline imaging before treatment and repeated imaging at 6-month intervals after the start of treatment.

RESULTS: All patients underwent follow-up imaging 6 months after the start of treatment; 25 patients, 12 months; and 10 patients, 18 months after the start of treatment. According to the Ishak histologic scoring system, nine patients had mild hepatitis; 30 patients, moderate to severe hepatitis; and eight patients, cirrhosis. Thirty-two patients responded to antiviral treatment. Among these patients, 25 had a decrease in PME/PDE ratio on follow-up imaging. Among responders the mean baseline PME/PDE ratio decreased from 0.27 +/- 0.02 (standard error) to 0.16 +/- 0.01 after treatment (paired Student's t test, p < 0.001). Among the 15 virologic nonresponders, the ratios were similar in six patients; six other patients had an increase on follow-up imaging. In the latter nonresponder group, the mean baseline PME/PDE ratio was 0.21 +/- 0.03 compared with 0.31 +/- 0.08 after treatment (paired Student's t test, p =0.24).

CONCLUSION: The in vivo hepatic PME/PDE ratio decreased in patients with hepatitis C who responded to antiviral treatment and remained similar or increased in patients without a virologic response. These results suggest that PME and PDE can be used as biomarkers in a noninvasive test of response to treatment.