Treatment monitoring with 18F-FDG PET in metastatic thymoma after 90Y-Dotatoc and selective internal radiation treatment (SIRT).

A 39 years old male patient with a history of an unresectable thymoma and synchronous liver metastases was referred tor our position. The patient had been originally treated with systemic chemotherapy followed by imatinib (Glivec) and sunitinib (Sutent). Since the therapeutic response was unsatisfactory, a gallium-68 ((68)Ga)-Dotatoc-positron emission tomography (PET) was performed and demonstrated an enhanced SSTR 2 expression in the primary tumor but not in the liver metastases. Three cycles of yttrium-90 ((90)Y)-Dotatoc were then administered. Outcome after treatment was monitored by (18)F-FDG-PET and CT and showed a response only of the primary tumor. Selective internal radiation treatment (SIRT) with (90)Y microspheres was then applied for the liver metastases. (18)F-FDG uptake showed that metabolism in the liver metastases decreased after SIRT. MRI of the liver demonstrated a decrease in vascularization and a modest decrease in tumor volume. Therefore, surgical resection of the primary thymoma was initiated.