31P MR spectroscopy to evaluate the efficacy of hepatic artery embolization in the treatment of neuroendocrine liver metastases

Background: It is common to treat patients with metastatic disease from gastrointestinal neuroendocrine (NE) tumors with surgical reduction to prolong survival. This can be combined with hepatic arterial embolization (HAE) and medical treatment to reduce hormonal symptoms. Today there are no rapid and reliable methods to evaluate the efficacy of HAE in the treatment of neuroendocrine liver metastasis. Purpose: To investigate metabolic changes in hepatic metastases of NE tumors following HAE, and to establish if there are any early spectral patterns that might indicate therapeutic efficacy based on in vivo P-31 MRS data. Material and Methods: Volume selective P-31 MRS was used to study 11 patients with disseminated NE tumors with regional lymph nodes and bilobar liver metastases. Measurements were performed before and 1 and 3 days after HAE. Results: Non-responders had significantly higher PME/Pi and alpha NTP/Sigma NTP ratios than the responders before HAE (P < 0.05). Three days after HAE, non-responders still had significantly higher alpha NTP/Sigma NTP than the responders did (P < 0.05). We also observed trends for increased PME ratios 3 days after HAE, decreased ATP-levels, and liberated Pi in responders. Conclusion: This P-31-MRS study showed significant differences in PME/Pi and alpha NTP/Sigma P,P ratios between responders and non-responders on the day before HAE, which is an interesting finding that may reflect intrinsic properties of the tumor tissue. We also observed trends for cell membrane renewal and increased energy consumption in responders after HAE. These results demonstrate potentials for P-31-MRS to predict individual responsiveness prior to HAE.