Thyroid cancer in the renal transplant population: epidemiological study

Abstract

The epidemiology of thyroid neoplasms in the renal transplant population has not been widely published. The present study compares the behaviour of thyroid cancer in the transplant cohort with that of the general population. It also documents the transplantation outcomes of patients with thyroid and non-thyroid cancers. All recipients of renal grafts are registered with the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry. Data were obtained from this institution and analysed using Microsoft Excel and Stata statistical software. Risk ratio, attributable risk, Mann-Whitney test, and the Kaplan-Meier survival probability were calculated. Between 1963 and 31 March 2002, 23 (0.22%) patients were diagnosed with thyroid cancer from a cohort of 10,689 renal transplant recipients. The median age in the renal-transplant thyroid cancer group was 48.2 years (range: 23-67 years), and there were 11 (48%) male patients, compared to 26% of thyroid cancer patients in the general population (P = 0.02). The median time to thyroid cancer diagnosis after transplantation was 68 months (range: 3-253 months) compared to 102 months (range: 3-363 months; P = 0.004) in non-thyroid cancers. Ten patients (43%) were found to have lymphatic metastasis, eight of whom presented at the time of primary diagnosis. The risk ratio (RR) was 5.2 (95% confidence interval: 2.0-16.6), with an attributable risk of 17.4 cases per 10,000. There were two cancer-related deaths resulting in a survival probability of 89% at 5, 10 and 15 years. There is a higher incidence of thyroid cancer and an altered sex distribution in the renal transplant population. A significant proportion presents with lymphatic metastasis requiring lymph node dissection and radioactive iodine treatment.