Influence of previous radiation exposure on pathologic features and clinical outcome in patients with thyroid cancer.

OBJECTIVE To determine whether previous radiation exposure to the head and neck is related to less favorable pathologic and clinical outcome in patients after surgical management of thyroid cancer. DESIGN Retrospective chart review. SETTING Academic teaching hospital (referral center). PATIENTS All patients with diagnosed thyroid cancer who had been exposed to radiation before surgical treatment were retrospectively identified from the thyroid cancer database at our institution (1963-2007). One hundred twenty-five patients (95 women and 30 men) were included. Inclusion criteria included surgical treatment for thyroid cancer and a history of exposure to radiation at least 3 years before diagnosis of the disease. MAIN OUTCOME MEASURES Pathologic features and data related to disease recurrence, distant metastasis, and survival. RESULTS Mean (range) age at first exposure to radiation was 19.4 (1-65) years, and mean lag time to diagnosis of disease was 28.7 (3-60) years. Patients were treated surgically with either total or near-total thyroidectomy (83%) or partial or subtotal thyroidectomy (17%). Pathologic diagnoses included 111 papillary carcinomas (89%). Sixty-three percent of patients had multifocal disease, 12% had lymphovascular tumor invasion, and 26% had direct extrathyroid extension of disease. Twenty-five percent of patients had metastases to cervical lymph nodes, and 9% had distant metastases. Sixteen percent of patients experienced local recurrence of disease. At last follow-up, 86% of patients were alive and free of disease, 8% were alive with disease, 4% had died of thyroid cancer, and 2% had died of an unrelated cause. Compared with other patients with thyroid cancer, this radiation-exposed cohort was more likely to undergo total thyroidectomy, multiple operative procedures, and external radiotherapy. A higher percentage had multifocal disease, extrathyroid extension, stage IV disease, and distant metastases. At follow-up, fewer patients were free of disease, and more patients had died of thyroid disease. CONCLUSION Patients who have been exposed to radiation have more aggressive disease and worse clinical outcome than other patients with thyroid cancer.