Younger kidney transplant recipients are at increased risk of cancer-related death compared with the general population, whereas older recipients are at lower risk, researchers have found.

Bryce A. Kiberd, MD, of Dalhousie University in Halifax, Nova Scotia, and collaborators analyzed data from 164,078 first kidney-only transplant recipients in the United States.

During a median follow-up of five years, 1,937 cancer-related deaths and 36,619 non-cancer deaths occurred. The observed cancer death rate was 206 per 100,000 patient-years compared with an expected rate of 215 per 100,000 patient-years in the general population, the investigators reported in the American Journal of Transplantation (2009;9:1868-1875).

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Overall, the age- and gender-adjusted standardized mortality ratio (SMR) was 0.96—suggesting no increased risk of cancer mortality—but SMRs varied by age group, with significantly higher and lower SMRs occurring in the youngest and oldest recipient populations, respectively.

Transplant recipients aged 19 years and younger and those aged 20-39 years had SMRs of 26.36 and 4.48, respectively. Among recipients aged 60-64, 65-69, and 70 and older, the SMRs were 0.81, 0.79, and 0.54, respectively.

“These findings challenge the notion that cancer is a major cause of premature death in all kidney transplant recipients and has implications for design of cancer prevention strategies in kidney transplant recipients,” the authors wrote.

Regarding the relatively high SMRs in the younger patients and the low SMRs in the older recipients, the researchers noted that one hypothesis is that competing risks of death from other causes “dampens the impact of immunosuppression-induced malignancy in the older transplant population.”

Supporting this hypothesis is the study’s finding that diabetes and prior history of congestive heart failure and stroke were independently associated with lower cancer mortality, the investigators noted. The higher SMRs in the younger recipients also support the hypothesis because these patients have lower competing risks of death and greater cumulative risks of succumbing to their cancers.

The authors observed that it is likely that better transplant care will translate into improved patient survival, resulting in increased proportions of patients who die from cancer.

They also suggested strategies to decrease cancer mortality, such as implementing screening strategies that are accepted in the general population, implementing new strategies for cancers that are dramatically increased in the transplant population, and decreasing the intensity or type of immunosuppression.

“Our findings suggest that it is the younger patients with longer expected life years after transplantation, with greater relative and cumulative risks of cancer death, that would ideally benefit from tailored immunosuppression,” the authors wrote.