Measurement of metabolite levels and treatment-induced changes in hepatic metastases of gastro-esophageal cancer using 7-T phosphorus magnetic resonance spectroscopic imaging.

Methods for early treatment response evaluation to systemic therapy of liver metastases are lacking. Tumor tissue often exhibits an increased ratio of phosphomonoesters to phosphodiesters (PME/PDE), which can be noninvasively measured by phosphorus magnetic resonance spectroscopy ( ³¹ P MRS), and may be a marker for early therapy response assessment in liver metastases. However, with commonly used ³¹ P surface coils for liver ³¹ P MRS, the liver is not fully covered, and metastases may be missed. The objective of this study was to demonstrate the feasibility of ³¹ P MRS imaging ( ³¹ P MRSI) with full liver coverage to assess ³¹ P metabolite levels and chemotherapy-induced changes in liver metastases of gastro-esophageal cancer, using a ³¹ P whole-body birdcage transmit coil in combination with a ³¹ P body receive array at 7 T. 3D ³¹ P MRSI data were acquired in two patients with hepatic metastases of esophageal cancer, before the start of chemotherapy and after 2 (and 9 in patient 2) weeks of chemotherapy. 3D ³¹ P MRSI acquisitions were performed using an integrated ³¹ P whole-body transmit coil in combination with a 16-channel body receive array at 7 T, with a field of view covering the full abdomen and a nominal voxel size of 20-mm isotropic. From the ³¹ P MRSI data, 12 ³¹ P metabolite signals were quantified. Prior to chemotherapy initiation, both PMEs, that is, phosphocholine (PC) and phosphoethanolamine (PE), were significantly higher in all metastases compared with the levels previously determined in the liver of healthy volunteers. After 2 weeks of chemotherapy, PC and PE levels remained high or even increased further, resulting in increased PME/PDE ratios compared with healthy liver tissue, in correspondence with the clinical assessment of progressive disease after 2 months of chemotherapy. The suggested approach may present a viable tool for early therapy (non)response assessment of tumor metabolism in patients with liver metastases.
(© 2024 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.)