Usefulness of (131)I-SPECT/CT and (18)F-FDG PET/CT in Evaluating Successful (131)I and Retinoic Acid Combined Therapy in a Patient with Metastatic Struma Ovarii

Abstract

Metastatic struma ovarii is an extremely rare disease, and the treatment of choice has not been established. Here, we introduce the case of a 36-year-old female pregnant patient with metastatic struma ovarii. Initial treatment was an exploratory laparotomy to remove multiple peritoneal masses. After delivery, a total thyroidectomy was done for the further (131)I-therapy. (131)I-SPECT/CT and (18) F-FDG PET/CT showed multiple hepatic metastases and extensive peritoneal seeding nodules. Multiple (131)I and retinoic acid combination therapies were performed, resulting in marked improvement. (131)I-SPECT/CT and (18) F-FDG PET/CT were quite useful for evaluating the biologic characteristics of the metastases.

Fig. 1

The first post-therapy ¹³¹I whole-body scan and ¹³¹I-SPECT/CT. a Post-therapy ¹³¹I whole-body images (30 mCi) show remnant thyroid glands. Intense iodine-avid lesions in the right lobe of the liver and multiple peritoneal seedings are well visualized. b Post-therapy ¹³¹I-SPECT/CT of the abdominopelvic cavity was obtained. The maximized intensity projection image is located in the left upper row. More prominent uptake in the multiple hepatic and peritoneal seedings is shown because of the longer acquisition time and three-dimensional modality. On the fusion axial image of ¹³¹I-SPECT/CT, hepatic metastases show iodine-avid uptake. Second and third row images show multiple peritoneal seedings with avid iodine uptake regardless of the small size (white arrow)

Fig. 2

¹⁸F-FDG PET/CT after the first ¹³¹I therapy. a Maximized intensity projection image shows hepatic metastasis in the right lobe of the liver and several seeding nodules with variable FDG uptake. b Fusion axial image shows a different glucose metabolism. The S5 lesion shows mild FDG uptake, but the S6 lesion shows intense FDG uptake. Multiple heptatic metastases were well correlated with MRI. c A small peritoneal seeding in the left iliac fossa shows increased uptake on the fusion PET/CT image and good enhancement on contrast-enhanced CT. d Intense uptake in the peritoneal seeding in the right pelvic side wall is visualized on the fusion PET/CT image. A round lesion with good enhancement is noted on contrast-enhanced CT

Fig. 3

The second post-therapy ¹³¹I whole-body scan and ¹³¹I-SPECT/CT combined with retinoic acid. a After the removal of hepatic metastases, post- ¹³¹I therapy a whole-body scan (200 mCi) was performed. More prominent uptake in the multiple peritoneal seedings is visualized in the perihepatic and abdominopelvic cavity. b ¹³¹I-SPECT/CT shows intense iodine uptake in the multiple peritoneal seeding nodules. A maximized intensity projection image of the abdominopelvic cavity is demonstrated in the left upper row. Fusion axial images of ¹³¹I-SPECT/CT reveal the location of peritoneal seedings in the perihepatic area, perigastric area, right and lower quadrant pelvic cavity, rectovaginal pouch, etc.

Fig. 4

The fifth post-therapy ¹³¹I whole-body scan and ¹³¹I-SPECT/CT. a Post-therapy ¹³¹I whole-body scan (200 mCi) reveals physiologic stomach and bowel uptake. Suspicious uptake is visualized in the pelvic cavity. b Fusion axial images of ¹³¹I-SPECT/CT show matched physiologic bowel uptake in the upper row and faint uptake in the previous seeding lesions in the pelvic cavity in the middle and lower row (white arrow). There was no significant lesion with avid iodine uptake. The patient showed a markedly improved state