Low-Dose Versus Standard-Dose Radioiodine Therapy in Differentiated Thyroid Cancer: Focus on Tolerability in a Retrospective Evaluation

Background: The role of radioiodine (RAI) therapy for differentiated thyroid cancers (DTCs) is still a matter of debate. Low-dose RAI (LDRAI) therapy is a possible treatment for patients at low-intermediate risk of recurrence. The aim of this study was to evaluate the occurrence of post-RAI therapy clinical and biochemical side effects with respect to its dosage. Methods: We retrospectively examined 142 patients who had been administered RAI therapy for DTCs and carried out at least a 12-month follow-up. The incidence of clinical adverse events (CAEs: xerophthalmia, xerostomia, and dysgeusia) and values for hemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs) and platelets (PLTs) during the first year of follow-up were compared between patients who underwent standard-dose RAI (SDRAI) therapy and LDRAI therapy. Results: Of the 142 patients, 66 were treated with LDRAI and 76 with SDRAI. A higher incidence of CAEs was found in the SDRAI group than in the LDRAI group (p = 0.002). An administered dose above 2849 MBq was associated with CAEs (sensitivity 88.89%, specificity 54.03%, p < 0.001). We found a slight decrease in Hb (p = 0.008), RBCs (p = 0.013), WBCs (p = 0.004) and PLTs (p < 0.001) in the SDRAI group, while in the LDRAI group only WBCs showed a minimal decrease (p = 0.027) with any occurrence of overt bone-marrow disease. Conclusions: According to our data, LDRAI therapy seemed to be associated with a lower incidence of CAEs than SDRAI therapy. Both methods showed an excellent safety profile in terms of hematopoietic effects. However, the effect of SDRAI therapy in this setting might have been more positive than that of LDRAI therapy.