Changing Paradigm in Treatment of Differentiated Thyroid Cancer

Abstract

Differentiated thyroid cancer is an indolent cancer with an excellent prognosis when treated adequately. The treatment algorithm is well established and standardized. Surgery followed by radio-iodine treatment has stood the test of time. In the last decade, the paradigm has slightly shifted with newer diagnostic approaches like stimulated thyroglobulin and anti-thyroglobulin antibodies impacting the treatment decisions. The diagnostic whole body radio-iodine scan has also got innovated with the introduction of r-TSH injection protocol wherein the scan is performed while the patient is on thyroxine thereby minimizing patient discomfort. The new RISK-based classification system has resulted in altered treatment algorithms by sub dividing patients into low-, intermediate-, and high-risk groups. There has also been identification of TWO new class of thyroid cancer patients-radio-iodine-resistant thyroid cancer and TENIS syndrome (thyroglobulin elevated negative iodine scan) patients. Both these groups posed major challenge to treatment and this resulted in incorporation of TARGETED THERAPY based on the mutations that occur in these TWO groups of patients. The introduction of Sorafenib and Lenvatinib has made significant impact on progression-free and overall survival of these patients. The introduction of THYROPET (124-I PET scan) is gaining momentum as an alternative to 123/131-I scans due to high-resolution images on PET scan increasing the detection sensitivity. All the above factors have resulted in paradigm shift in the management of differentiated thyroid cancer patients.

Keywords: Recombinant TSH; Stimulated thyroglobulin (Tg); TENIS syndrome; Targeted therapy.

Fig. 1

A Patient with papillary cancer thyroid cancer with raised anti-thyroglobulin antibody and normal thyroglobulin level shows post-op residual thyroid tissue in the neck. B Radio-iodine scan 8 months after 131-I therapy shows complete ablation of neck disease

Fig. 2

A Radio-iodine scan after 2 injections of r-TSH shows extensive pulmonary metastases and neck tissue. B Radio-iodine scan 8 months after treatment with 150 millicurie of radio-iodine with TWO injections of r-TSH shows almost complete ablation with TWO residual areas in chest

Fig. 3

A Post-surgery radio-iodine scan shows NO radio-iodine uptake with Thyroglobulin level of 22 ng/ml and TSH 80 microunits/ml. B FDG PET scan showed right supra clavicular and right paratracheal node abnormality

Fig. 4

¹²⁴I PET scan [13]. A Pre-therapy 124-I PET scan shows discrete focal lesions in right femur along with neck and mediastinal nodes. B Post therapy 131-I scan shows lesser lesions with diffuse uptake pattern

Fig. 5

The chest X-ray and CT scans show regression of pulmonary infiltrates after 6 months of lenvatinib therapy [17]