Prognostic Factors Affecting Disease-Specific Survival in Patients with Recurrent and/or Metastatic Differentiated Thyroid Carcinoma Detected by Positron Emission Tomography/Computed Tomography

Abstract

Aim:

We aimed to analyze the prognostic factors affecting disease-specific survival in patients with recurrent and/or metastatic differentiated thyroid carcinoma.

Methods:

Seventy-seven patients with recurrent/metastatic differentiated thyroid carcinoma who were previously treated with total thyroidectomy followed by radioactive iodine therapy were enrolled. Recurrent/metastatic disease was detected by positron emission tomography/computed tomography. At the time of last follow-up (mean 4.8±1.3 years), patients were grouped as having (i) clinical remission (n=17), (ii) stable disease (n=22), or (iii) progressive disease (n=38). We retrospectively examined the prognostic impact of clinical factors (age, sex, TNM stage), histopathological factors of the primary tumor (tumor size, histology, the presence of vascular invasion, extrathyroidal spread, and lymph node metastasis), serum thyroglobulin levels, and metabolic parameters of recurrent/metastatic disease such as radioactive iodine avidity, F18-fluorodeoxyglucose uptake (SUV_max) in metastatic deposits, number and location of F18-fluorodeoxyglucose–avid lesions (locoregional vs. distant), and the impact of surgery on disease-specific survival.

Results:

Lack of vascular invasion (p=0.04), presence of surgically amenable recurrence/metastasis (p=0.0001), and suppressible on-therapy serum thyroglobulin levels at the time of recurrent/metastatic disease (p=0.01) were strong predictors of clinical remission and good prognosis on multivariate analysis. Lesional SUV_max, number or location of F18-fluorodeoxyglucose–avid lesions, and TNM stage did not correlate with clinical outcome. Clinical remission could only be achieved by curative surgery. Patients without curative surgery for recurrence/metastasis had a 43 times higher risk to develop progressive disease than patients with disease amenable to surgery.

Conclusions:

Curative surgery is an essential therapeutic modality to achieve clinical remission in metastatic/recurrent differentiated thyroid carcinoma. Positron emission tomography/computed tomography is a powerful method to detect surgically resectable disease for the selection of patients who may benefit from curative surgery.