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February 15, 2012

Cancer Risk After Organ Transplantation—Reply

Author Affiliations

Author Affiliations: National Cancer Institute, Rockville, Maryland (Drs Engels and Pfeiffer) (engelse@exchange.nih.gov); and Scientific Registry of Transplant Recipients, Minneapolis, Minnesota (Dr Kasiske).

JAMA. 2012;307(7):663-664. doi:10.1001/jama.2012.141

In Reply: Dr Vajdic and colleagues point out that cancer risk in transplant recipients can appear artifactually high if prevalent cancers are inadvertently attributed to the posttransplant period. This situation could arise from delayed cancer diagnosis or reporting to cancer registries. Such delays would usually be short and mostly affect risk estimates in the first months after transplantation.

Because our study described results for almost 50 different malignancies, we used a uniform approach to assess risk in transplant recipients. Follow-up time began at transplantation. In their previous study of cancer risk in Australian kidney recipients, Vajdic et al1 took the same approach and began follow-up at transplantation. This decision is appropriate for both studies because it is important to capture the high risk for some malignancies (eg, non-Hodgkin lymphoma) that arise immediately after transplantation due to the intensity of immunosuppression and newly acquired viral infections. Additionally, transplant candidates are carefully screened before listing, and given the risk of cancer progression with administration of immunosuppressive medications, most people with recent cancer would not be considered for transplantation. Thus, for most cancers, there would be few prevalent cases that might later be mistaken for incident cases.