The goals of post-surgical RAI therapy in patients with differentiated DTC are to ablate residual normal thyroid tissue that may facilitate surveillance,) Also the potential tumoricidal effect on residual microscopic RAI-avid disease, and to provide a posttreatment whole-body scan that may reveal undetected local or distant metastases.Although, these goals are important, the ultimate endpoint of postsurgical ablation is to minimize DTC recurrence and death by eliminating residual normal thyroid tissue or residual microscopic disease that could be a focus for future recurrence(1). Successful RAI-131 thyroid remnant ablation is associated with better prognosis with regard to both recurrence-free and overall survival, lower rates of distant metastases, and reduced cancer mortality rates, compared with only surgery or surgery and L-thyroxin therapy alone (2). It also facilitates long-term follow up of patients with DTC. It was shown by
Verburg et al. that a successful ablation itself seems to be a highly important prognostic factor for long-term outcome. They found that the patients with a successful ablation, 87% were still free of the disease after 10 years, whereas of the patients with an unsuccessful ablation, only 50% were free of disease with thyroid cancer-related survival was (93% versus 78%) (P > 0.001)(3). After four decades of follow-up, based on regression modeling of 1510 patients without distant metastases at the time of initial therapy,
Mazzaferri and Kloos found thyroid remnant ablation to be an independent variable that reduced loco regional recurrence, distant metastases, and cancer death. A similar observation has also been made by the National Thyroid Cancer Treatment Cooperative Study group (4), they had reconfirmed that postoperative RAI treatment was associated with improved cancer-specific mortality rates and reduced disease progression in both papillary and follicular cancer(5).