Low dose radioactive iodine ablation therapy (1.11GBq) for differentiated thyroid cancer in Western Turkey

Ablation therapy is employed in low-risk differentiated thyroid cancer (DTC) cases to facilitate patient monitoring by reducing thyroglobulin (Tg) levels to measurable levels below after surgery by eliminating residual thyroid tissue. However, there is still uncertainty about the minimum activity dose required for effective ablation. Opting for low-dose [131I]-NaI for ablation offers several advantages for both patients and healthcare services. Particularly in this tumor group with a high life expectancy (approximately 90-95 % at 10 years), [131I]-NaI treatment should not pose a risk to the patient's post-treatment life and should not compromise their quality of life. However, there is a need for a well-defined identification of factors predicting successful ablation.

Clinical data, laboratory findings, and imaging tests of 287 patients with low-dose 1110 MBq (30 mCi) [131I]-NaI ablation therapy for DTC were retrospectively reviewed. Post-ablation imaging and laboratory findings categorized ablation success/failure. The successful ablation group was determined according to the excellent response criteria outlined in ATA criteria. Relationships between clinical, pathological findings, biochemical common variables, and treatment failure were analyzed.

An excellent response was achieved in 77% of the entire group according to ATA criteria post-ablation. Male gender and high Tg levels on the day of ablation (Tg cut-off: 10 ng/mL and 5.35 ng/mL) were associated with unsuccessful ablation.

Our results indicate that a 1110MBq (30mCi) ablation dose is sufficient to achieve an excellent response in most low-risk DTC cases 6-12 months later. When selecting the dose for ablation, besides the histological markers mentioned in guidelines and age, we observed that stimulated Tg values and gender may be important in predicting ablation success.