Pretargeted radioimmunotherapy in rapidly progressing, metastatic, medullary thyroid cancer.

Medullary thyroid cancer (MTC) patients with localized residual disease and/or distant metastases may survive for several years or rapidly progress and die of their disease. Thus, highly reliable prognostic factors are needed for an early distinction between high-risk patients who need to be treated and low-risk patients who warrant a watch-and-wait approach. Calcitonin doubling time is an independent predictor of survival, with a high predictive value in a population of patients who have not normalized their calcitonin, even after repeated surgery. Several imaging methods should be proposed for patients with abnormal residual calcitonin levels persisting after complete surgery: ultrasonography and computed tomography (CT) for neck exploration, and CT for chest, abdomen, and pelvis. Magnetic resonance imaging (MRI) appears to have an advantage over CT for the detection of liver metastases from endocrine tumors. Moreover, MRI appears to be a sensitive imaging technique for detecting the spread of MTC to bone/bone marrow. 2-Fluoro-2-deoxy-D-glucose positron emission tomography/CT could be used for staging patients with progressive MTC, with possible prognostication by standard uptake value quantification. For systemic treatment of patients with rapidly progressing metastatic MTC, chemotherapy is not considered a valid therapeutic option. It is too early to evaluate the potential effectiveness of multikinase inhibitors, although interesting results of phase 2 studies have shown a transient stabilization in 30% to 50% of patients. Pretargeted radioimmunotherapy has been the only innovative treatment modality convincingly showing some survival benefit when compared with a historical untreated control group.