Incremental value of post-high dose therapy I-131 scan over pre.therapy diagnostic I-131 scan in patients with differentiated thyroid cancer: Experience from a tertiary care centre in South India

Objective: Objective of this study is to establish the incremental value of post-high dose therapy I-131 whole body scintigraphy (WBS) over diagnostic pre-therapy I-131 WBS in the detection of radioiodine avid foci, staging and change in the management in patients with differentiated thyroid carcinoma post-total thyroidectomy. Methods: We retrospectively studied 93 post-total thyroidectomy patients with well differentiated thyroid cancer (mean age 47 [range 18–78] years; 72 females) who underwent diagnostic dose pre-therapy? I-131 WBS and post-high dose therapy? I-131 WBS from January 2017 to June 2018 were included. Discordance rate of pre-therapy? I-131 WBS findings with post-therapy? I-131 WBS was calculated. Results: Post-therapy I-131 WBS revealed additional radioiodine avid foci not detected on pre-therapy? I-131 WBS in 16 (17.2%) patients. Upstaging was more common in patients =55 years (8 of 23, 34.8%) when compared to patients Conclusion: Post-therapy? I-131 WBS revealed new foci in 17.2% patients and clinical upstaging occurred in 9.6% of patients compared to pre-therapy I-131 WBS. There is a significant improvement in the detection of radioiodine avid foci overall and also metastatic lymph nodes by doing post-therapy? I-131 WBS. We suggest that post-therapy? I-131 WBS should be routinely done as it had an incremental role over pre-therapy? I-131 WBS in establishing the true extent of tumour burden, in upstaging the disease and thereby planning adequate hormone suppression to attain target thyroid stimulating hormone levels.