sup 124^I PET-Based 3D-RD Dosimetry for a Pediatric Thyroid Cancer Patient: Real-Time Treatment Planning and Methodologic Comparison

Patient-specific 3-dimensional radiobiologic dosimetry (3D-RD) was used for ^sup 131^I treatment planning for an 11-y-old girl with differentiated papillary thyroid cancer, heavy lung involvement, and cerebral metastases. ^sup 124^I PET was used for pharmacokinetics. Calculation of the recommended administered activity, based on lung toxicity constraints, was performed in real time (i.e., during the data-acquisition interval). The results were available to the physician in time to influence treatment; these estimates were compared with conventional dosimetry methodologies. In subsequent, retrospective analyses, the 3D-RD calculations were expanded to include additional tumor dose estimates, and the conventional methodologies were reexamined to reveal the causes of the differences observed. A higher recommended administered activity than by an S-value-based method with a favorable clinical outcome was obtained. This approach permitted more aggressive treatment while adhering to patient-specific lung toxicity constraints. A retrospective analysis of the conventional methodologies with appropriate corrections yielded absorbed dose estimates consistent with 3D-RD. [PUBLICATION ABSTRACT]