Thallium-201 scintigraphy in pediatric soft-tissue tumors

Thallium-201 has been used as a tumor imaging agent in adults with lymphoma, brain tumors, thyroid carcinoma and bone sarcomas. The application of 201Tl in pediatric oncology has been very limited.

Whole-body 201Tl studies were incorporated into the imaging protocols of 45 children with solid soft-tissue tumors. Bone and 67Ga scans as well as 131I-MIBG scans for patients with neuroblastoma were obtained.

Seventeen children with lymphoma, five with Hodgkin's disease and twelve with non-Hodgkin's lymphoma (NHL) were studied. All of the patients with Hodgkin's disease showed avid uptake of 201Tl and 67Ga. The six patients with B-cell NHL had positive 67Ga scans and four had positive 201Tl scans. There was variable uptake in T-cell and undifferentiated lymphoma with an overall sensitivity of 69% for 201Tl and 85% for 67Ga. In 14 patients with rhabdomyosarcoma, 10 (71%) had positive 201Tl scans and 11 (79%) had positive 67Ga images. Gallium and thallium scans detected lesions equally. There was poor uptake of 201Tl in the six children with neuroblastoma. Primary tumor and metastases were detected more readily with the bone and MIBG scans. Three children with Wilms' tumor had poor or no uptake on 201Tl images, two of three patients with histocytosis had no significant uptake and one patient had mild uptake of 201Tl. One patient with primitive neuroectodermal tumor had positive 201Tl and 67Ga images and one patient with a neurofibrosarcoma had negative 201Tl and 67Ga images. There was no correlation with histological types of tumor or disease staging.

This study shows significant uptake of 201Tl in many pediatric solid soft-tissue tumors. Additional study is needed to determine 201Tl effects on treatment response and tumor viability. Also, more studies are needed to assess 201Tl delayed images to determine if there is more tracer concentration in the tumors.