Thyroid cancer and renal transplantation: a meta-analysis

Kidney transplantation and the associated immune suppression are associated with a significantly increased risk of developing cancer during long-term follow-up. Thyroid cancer has been recognised as a potential post-transplant risk but has not yet been subject of a focused review. We therefore performed a meta-analysis on data of 50,861 patients with a total follow-up of 198 595 patient-years and identified a 6.9-fold higher standardised incidence ratio (95% confidence interval 5.6-8.7, P<0.001) of thyroid cancer post renal transplantation as compared with a non-transplant group. All such cancers were of papillary type as far as histopathology was known. The mean time to discovery was 6.0 years post transplantation. This puts thyroid cancer into the group of high cancer risk following solid organ transplantation which already includes cervical cancer, non-melanoma skin cancer, oral and lip cancer and haematological malignancies. It is unclear what causes the increased cancer incidence. Inclusion of thyroid ultrasound in long-term post-transplant evaluation may help to ensure timely recognition of this condition.