Response to Therapy Assessment in Differentiated Thyroid Cancer patients submitted to Total Thyroidectomy or Lobectomy Without Radioactive Iodine Therapy
Denise P Momesso1, Mario Vaisman1, Rossana Corbo1, Samantha P Yang2, R. Michael Tuttle1, Fernanda Vaisman2
1 Endocrinology Department, Universidade Federal do Rio de Janeiro (UFRJ) and Instituto Nacional do Cancer (INCA), Rio de Janeiro, Brasil.
2 Endocrinology, Memorial Sloan Kettering Cancer Center, New York, USA.
Introduction: While response to therapy assessment is a validated tool for ongoing risk stratification in differentiated thyroid cancer (DTC) patients submitted to total thyroidectomy (TT) and radioactive iodine therapy (RAI), it has not been well studied in patients treated with lobectomy (L) or TT without RAI. Because the response to therapy definitions are heavily dependent on serum thyroglobulin (Tg) levels, modifications of the original definitions were needed to appropriately classify patients treated without RAI. The aim of this study was to evaluate and validate these previously proposed response to therapy definitions in DTC patients submitted to L or TT without RAI.
Methods: 507 adults with DTC submitted to L (n=187) or TT (n=320) without RAI were retrospectively evaluated.
Results: Median age was of 43.7 years, 88% were female, 85% had low and 15% intermediate ATA risk. During follow-up period (median 100.5 months) recurrent/persistent structural disease (SD) was diagnosed in 3.6% of the patients. All patients (100%) classified as having excellent response to therapy (non-stimulated Tg for TT <0.2ng/ml and for L < 30ng/ml; n=326) had no evidence of SD at final follow-up. SD was observed in 1.3% of the patients with indeterminate response (non-stimulated Tg for TT 0.2-5ng/ml, stable or declining Tg antibody and/or non-specific findings on imaging; n=2/152); 31.6% of patients with biochemical incomplete response (non-stimulated Tg for TT >5ng/ml and for L >30ng/ml and/or increasing Tg antibody and negative imaging; n=6/19) and all (100%) patients with structural incomplete response (n=10/10) (p<0·0001). Initial ATA risk estimates were significantly modified based on response to therapy assessments, since excellent response to therapy significantly decreased the risk of SD to 0% and incomplete response (biochemical or structural) increased the risk of SD.
Conclusions: Our data validates the newly proposed response to therapy assessment in DTC treated with L or TT without RAI as an effective tool for ongoing risk stratification that could be used to modify initial risk estimates and better tailor follow-up and future therapeutic approaches.
Keywords: (5) response to therapy assessment; differentiated thyroid cancer; total thyroidectomy without radioactive iodine; lobectomy.