Risk Factors for Nonremission and Progression-Free Survival after I-131 Therapy in Patients with Lung Metastasis from Differentiated Thyroid Cancer: A Single-Institute, Retrospective Analysis in Southern China

OBJECTIVE:Prognostic factors related to progression-free survival (PFS) have not received much attention in the literature regarding iodine-131 ((131)I) therapy for patients with differentiated thyroid cancer and lung metastases. We sought to explore the factors associated with PFS and nonremission in a group of patients with differentiated thyroid cancer and pulmonary metastases at initial diagnosis and to investigate the impact of (131)I therapy on pulmonary function and peripheral blood counts in the same cohort of patients.METHODS:The medical records of 1,050 patients with differentiated thyroid cancer treated at the Zhujiang Hospital of Southern Medical University from January 2006 to January 2015 were retrospectively reviewed. Among them, 107 patients fulfilled the inclusion criteria.RESULTS:Multivariate Cox regression analysis indicated that age ≥45 years and (131)I nonavidity were independent risk factors for disease progression. Multivariate logistic regression analysis revealed that pulmonary nodule size ≥1 cm and (131)I nonavidity were the strongest risk factors predicting nonremission. Varying cumulative (131)I dosage had no association with posttreatment pulmonary function or peripheral blood cell counts.CONCLUSION:Similar to earlier studies, our results confirm that (131)I nonavidity was associated with an increased risk of disease progression and greater odds of nonremission. In addition, patients with differentiated thyroid cancer and lung metastases with pulmonary nodules ≥1 cm had a reduced likelihood of achieving remission. Furthermore, special attention is needed when monitoring patients over 45 years at a higher risk of disease progression.ABBREVIATIONS:CI = confidence interval DTC = differentiated thyroid cancer (18)F-FDG = fluoro-18 fluorodeoxyglucose FEF = forced expiratory flow FTC = follicular thyroid cancer FVC = forced vital capacity GR = granulocytes Hb = hemoglobin HR = hazard ratio (131)I = iodine-131 LN = lymph node OR = odds ratio OS = overall survival PET/CT = positive positron emission tomography/computed tomography PFS = progression-free survival PT = partial thyroidectomy PTC = papillary thyroid cancer RAI = radioactive iodine RBC = red blood cell Tg = thyroglobulin TgAb = thyroglobulin antibody TSH = thyroid-stimulating hormone TT = total thyroidectomy WBC = white blood cells WBS = whole body scan.