131I treatment response in thyroid neoplasms and evaluation of radiation dose complications. A review of ten years of experience

Full text: Thyroid cancer (TC) is the most common endocrine malignancy, but its management is still a controversial issue that included an interdisciplinary approach who compounds surgery, radioiodine (RAI) therapy and sometimes external radiation therapy. The aim of our work is to evaluate the role of the RAI treatment in well differenciated thyroid carcinoma and its implication in terms of survival and complications. Methods and Material: we collected data from medical records of 215 patients with confirmed TC, registered from 1990-2004 at the Nuclear Medicine Unit, Hospital Temuco, Chile, who received 50 to 150 mCi RAI therapy four to six weeks after lobectomy, partial or total thyroidectomy. Clinical and laboratory examinations were analyzed including blood count, thorax X Ray, whole body I-131 scans, and serum thyroglobulin. Results: the median age at the diagnosis was 51 years, there were 89% females. All patients were treated surgically and recived postoperative RAI treatment. Total thyroidectomy, subtotal thyroidectomy and nodule excision was done in 69%, 31% and 37% of patients respectively. The histopathologic results included papillary (62%), follicular (24%) and papillary-follicular carcinoma (14%). Regional lymph nodes were positive in 36% and distant metastases were detected in 20 %, located in the lungs in all of those patients. Additional RAI doses between 100-200 mCi were administrated in 35% patients after to wait a period longer than 1 year. The overall survival rate at 14 years was 93 %, and recurrent disease was detected in 15%. at 5 years and 20% at 14 years from the diagnosis. There were no major complications and minimal alterations in the blood count was observed. We conclude that total or near total thyroidectomy followed by RAI treatment appears to benefit for better survival and lower recurrence disease. Favorable prognostic management included radioiodine therapy at the primary treatment using high actvities (more than 100 mCi) after total or near total thyroidectomy. Additional pulmonary metastases did not influence prognosis, and secondary effects were mild and related to the symptoms of hypothyroidism. (author)