White Race As a Risk Factor for Hypothyroidism After Treatment for Pediatric Hodgkin's Lymphoma

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Abstract
Purpose: Hypothyroidism frequently occurs after treatment for pediatric Hodgkin's lymphoma, but race has not been investigated as a risk factor for this delayed toxicity. The aim of this study was to determine whether race is an independent risk factor for hypothyroidism in survivors of pediatric Hodgkin's lymphoma. Patients and Methods: To identify differences between black and white patients in the development of hypothyroidism after treatment for Hodgkin's lymphoma, we conducted a retrospective study of consecutively treated pediatric patients with newly diagnosed Hodgkin's lymphoma treated at St Jude Children's Research Hospital (Memphis, TN) from January 1980 through December 2002. Clinical or biochemical hypothyroidism was defined by an above normal thyroxine-stimulating hormone concentration or by the need for thyroid hormone replacement therapy. Results: The 461 patients (388 white patients, 73 black patients) where followed for a median of 11.3 years (range, 1.8 to 24.9 years). Hypothyroidism developed in 196 (43%) of 461 patients after a median of 2.9 years (range, 0.7 to 11.3 years) after diagnosis of Hodgkin's lymphoma. Hypothyroidism developed in 47% of white patients but in only 21% of black patients (hazard ratio = 2.7; 95% CI, 1.6 to 4.6). After adjusting for other risk factors for hypothyroidism (thyroid radiation dose, sex, and nodular sclerosis histology), the risk of hypothyroidism in white patients was 2.5 times (95% CI, 1.5 to 4.3 times) the risk in black patients (P < .001). Conclusion: White patients have a higher risk of hypothyroidism after neck irradiation for pediatric Hodgkin's lymphoma than black patients.