The problem of the patient with thyroglobulin elevation but negative iodine scintigraphy: the TENIS syndrome

The available data upon which to act in caring for patients with functioning thyroid cancer and thyroglobulin elevation/negative iodine scintigraphy (TENIS) are imperfect, almost never coming from randomized, blinded studies. When the serum thyroglobulin exceeds 2-10 ng/mL, one should use the latest imaging equipment available to find metastatic disease, especially in areas in which it is potentially resectable, ie, neck, bone, and occasionally brain, and collaborate with an experienced surgeon in removing such metastases. If one cannot locate operable metastases and/or tumor location remains elusive, empiric high-dose (131)I therapy, preceded by dosimetry, should be considered. There are no randomized studies to prove that this treatment prolongs life, although there is definite evidence of cell killing, because the serum thyroglobulin level frequently diminishes after radioiodine therapy. In selected cases External beam radiotherapy will be helpful when the tumor has been located but cannot be fully removed, for example, with invasion of the trachea, spine, or muscles. There are several tyrosine kinase inhibitors that have shown some effectiveness against the TENIS syndrome, but these should ideally be used in the context of a clinical trial. Tyrosine kinase inhibitor drugs should be preferred to conventional chemotherapy at this time; data on lenalidominde have only appeared in abstract form. The return of NIS function, to permit functioning thyroid cancer with the TENIS syndrome to again concentrate therapeutic amounts of (131)I, remains an elusive goal, with few drugs showing real promise. Gene therapy to restore the function of the NIS gene and enhance cellular immunomodulatory and tumor suppressive activity has not yet succeeded clinically. Physicians caring for patients with the TENIS syndrome are urged to enter them into clinical therapeutic studies whenever possible.