Diet low in iodine as well as goitrogens (LILGD) enhanced radioiodine (I-131) uptake in treatment of differentiated thyroid cancer

Full text: Low iodine diet (LID) is accepted as an adjuvant to post-thyroidectomy radioiodine therapy of differentiated thyroid cancer since it is held to enhance radioiodine uptake in thyroid remnants and thyroid cancer tissue. However, in the few clinical investigations performed only an indirect and weak evidence of a positive effect of the LID has been demonstrated. Also we had discouraging experience in the application of a strict LID using the same design as in the present study. We therefore decided to investigate the effect of a diet low in iodine as well as in goitrogens (LILGD). Methods: Six patients with differentiated thyroid cancer entered the study and they were their own control. After thyroid hormone withdrawal (TSH > 30 m U/L) and on regular diet a diagnostic whole body scan was performed 24 h after administration of 50 MBq (1,4 mCi) 123I. The day following diagnostic scan the patients were put on LILGD for 4 days prior and two days after radioiodine therapy. In LILGD beverages, fruits and vegetables containing flavonoids, glucosinolates, cyanides and thiocyanates were avoided and spices and smoking prohibited. Therapeutic radioiodine was administered one week after diagnostic procedures and in the morning after over-night fasting with an activity range of 3,7-5,4 GBq (100 -150 mCi) 131I. A 24-h therapeutic whole body scan and calculations of percentage uptake U(24) were performed. Diagnostic (basal) D U(24)% and subsequent therapeutic T U(24)% uptake were compared and expressed as therapeutic/diagnostic uptake ratios T/D U(24). Results: A significant increase in therapeutic versus diagnostic uptake T/D U(24) was observed (mean 2,53, median 2,30, range 1,40 - 4,46, p<0,02, n=6). Conclusion: Taking account of iodine as well as goitrogens in the diet (LILGD) a simple and low-cost measure, has a significant positive effect on 131I uptake in radio-ablation of normal and thyroid cancer tissue. (author)