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Survival Analysis of 19 Patients with Toxic Thyroid Carcinoma

Institutes of Pathology (C.A., P.G., J.A.L.), Clinical Chemistry (C.A.), Internal Medicine (P.N.), and Nuclear Medicine (H.R.), Inselspital, Institute of Social and Preventive Medicine (C.M.), University of Bern, CH-3010 Bern, Switzerland; and Institute of Nuclear Medicine (C.A.), Clinique Ste. Therese, L-2763 Luxembourg, Luxembourg

Address all correspondence and requests for reprints to: Claudine Als, M.D., Division of Clinical Chemistry, Inselspital, University of Bern, CH-3010 Bern, Switzerland. E-mail: . claudine.als{at}insel.ch

Abstract

Among patients with differentiated thyroid carcinoma (diffTCa), the rare hyperfunctioning or toxic TCa (ToxTCa) was diagnosed when scintigraphic hot thyroid areas were attributable only to diffTCa (diameter >1 cm by pathological examination) and/or total thyroidectomy failed to induce hypothyroidism. Of 924 cases of all TCa (papillary diffTCa 47.3%, follicular diffTCa 44.2%, others 8.5%), 19 had ToxTCa (2.1%, 15 of 19 follicular, 4 of 19 papillary, P = 0.008). These received a more intensive radioiodine therapy (average cumulated ¹³¹I activities 21.8 vs. 15.2 GBq, P < 0.01). Five-year survival rates for ToxTCa (n = 19, 56%) and diffTCa (n = 545, 94.5%) differed [hazard ratio 4.8, 95% confidence interval (CI) 2.8–8.1, P = 0.001]. However, the differences were attenuated by matching ToxTCa and diffTCa (n = 57, 5-yr survival rate 74%) for age, sex, and histopathologic type (hazard ratio 2.1, 95% CI 1.13–3.9, P = 0.02). Correcting statistically for M₁ against M₀ stage distribution resulted in a further reduction of the hazard ratio (hazard ratio 1.8, 95% CI 0.93–3.48, P = 0.08). An M₁ stage is an important prognostic factor in ToxTCa patients. Thus, ToxTCa, treated with higher activities of ¹³¹I, has a survival prognosis close to that of matched diffTCa cases, both groups consisting mainly (79%) of follicular subtypes.