Background: The kidney recipient is at a higher risk for cancer than is the general population, although the incidence of neoplasms in general is considered lower in Japan than in Western countries. The cause of this increased risk associated with either transplantation or geography has not yet been established.
Method: The incidences and sites of malignant neoplasms were analyzed in 285 kidney recipients, who had been followed up for 3007 patient-years. The relationship between immunosuppressive states, the numbers of CD4-positive T lymphocytes, and the presence of malignant neoplasms was studied retrospectively.
Results: Eighteen malignant neoplasms were found in 1 7 of the 285 patients (6%). The malignancies developed in these patients an average of 1 26.5 months aftertransplantation. The incidencewasonly3.9% at 1 0 years, increasing to1 3.9% at 20 years. No difference in the time-course incidence was found between azathioprine-based and cyclosporin-based immunosuppressive regimens. The malignancies developed in the digestive organs in more than half of the patients, and were mainly in the liver, colon and rectum, and stomach, with a relatively low incidence of skin cancer and lymphoma. There was only one case of Epstein-Barr virus genome found in 5 specimens that were tested. Concerning the immunosuppressive state, CD4-positive T lymphocyte counts were not related directly with malignancies in our series.
Conclusion: The cumulative incidence of malignancy increased markedly in the second posttransplant decade. The site of cancers in kidney recipients mirrors that of general Japanese malignancies. Our results revealed neither the cause nor predictor for malignancies in kidney transplant patients.