Management of 131I therapy for thyroid cancer: cumulative dose from in-patients, discharge planning and personnel requirements.

AIM: To provide a comprehensive overview with regard to the hospitalization/discharge planning and nursing staff requirements for the management of patients treated with radioiodine for differentiated thyroid carcinoma. METHODS: A statistical analysis of the fast clearance phase of 131I was performed in 265 hospitalized patients treated after total thyroidectomy with fixed doses ranging from 2590 to 9250 MBq. RESULTS: Two hundred and twenty-five cases were post-surgical ablation treatments and 40 cases were follow-up treatments. The 131I clearance was studied during hospitalization of 2-4 days. No clearance differences were found between the two groups. The median value of the biological half-time (T1/2bio) was 0.65 days, with a variability range of 0.30-2.03 days. A statistical model for the distribution of T(1/2bio) was reported. Some patients on maintenance haemodialysis were also studied, with T(1/2bio) values ranging from 1.6 to 2.6 days. The weekly cumulative dose to personnel from external exposure, corresponding to the 95th percentile, ranged from 0.1 mSv per GBq of administered activity (mSv x GBq(-1)) with a totally ambulant patient to 5.4 mSv . GBq with a totally helpless patient. With patients on maintenance haemodialysis, these values could increase from 1.2 to 1.7 times. The cumulative dose to close relatives was also estimated. The hospitalization times associated with 75% and 95% probabilities of patient discharge were calculated by varying the residual activity limit from 100 to 800 MBq. Finally, using the median T(1/2bio), personnel requirements were evaluated. With totally ambulant and semi-ambulant patients, about 0.5 and 1.0 personnel units per GBq of weekly administered activity were needed so as not to exceed an annual planning dose of 6 mSv per year. The treatment of patients with higher degrees of dependency was impractical. CONCLUSIONS: On the basis of statistical analysis, a better organization of in-patient treatment may be obtained, as well as more accurate preliminary evaluations of the cumulative doses to nursing staff and attending personnel, for the management of patients treated with radioiodine for differentiated thyroid carcinoma.