Abstract:
Background: Recurrence of Well-differentiated thyroid cancer (WDTC) occurs in 6-30% of patients, commonly loco-regional recurrence. Aim: To explore recurrence patterns in WDTC patients, identifying variables linked to different relapse patterns. Patients & Methods: We retrospectively analyze data of50 patients with WDTC who developed recurrence post successful complete ablation. Results: 58%, 38%, and 4% of patients developed loco-regional, mixed, and metastatic relapse respectively. Cervical lymph nodes and lungs are the commonest sites of loco-regional and metastatic relapse. 72% of recurrence occurred at 5-years post diagnosis.Recurrence was more encountered in old males and follicular carcinoma. All patients had two or more unfavorable pathological prognostic factors. Development of distant metastases is significantly more in males, high risk patients, follicular carcinoma, presence of capsular and vascular invasion, multifocality together with failure of complete ablation post single 131I ablation dose and higher sTg at time of recurrence diagnosis. 11patients lose ability to concentrate 131I, solely, associated significantly with presence of higher sTg level on relapse diagnosis. FDG PET/CT localized recurrence site in 10 out of those 11 patients. Conclusion: Loco-regional recurrence is the commonest form of recurrence followed by mixed and metastatic relapse.72%of relapse occurred 5-years post-initial diagnosis. Cervical lymph nodes and lungs are the commonest sites of loco-regional and metastatic relapse. Dedifferentiation of recurrence occurs in around one fifth of patients, FDG PET/CT sensitivity for localization of relapse site in patients with dedifferentiation is 90%. Distant metastases is significantly more encountered in males, follicular carcinoma , presence of capsular or vascular invasion and multifocality, together with failure to achieve successful complete ablation post first 131I ablative dose and in presence of higher sTg at time of diagnosis of recurrence. The latter is the sole factor that appears to be more significantly associated with occurrence of dedifferentiation.