A 30-Year Analysis of Colorectal Adenocarcinoma in Transplant Recipients and Proposal for Altered Screening

The risk of malignancy after solid-organ transplantation is well documented. However, the incidence and specific risk for colorectal adenocarcinoma, although previously proposed, has been difficult to calculate. We reviewed the University of Wisconsin transplant database for all cases of colorectal adenocarcinoma to assess the risk of this malignancy, as well as the need for improved screening in this population.

The transplant database was queried using diagnosis codes for colorectal adenocarcinoma to configure a list of eligible patients. Exclusion criteria included: age less than 18 years at the time of transplant, diagnosis of colorectal cancer or patient death less than 12 months posttransplant, and pretransplant history of colorectal cancer or proctocolectomy. Statistical analysis determined overall incidence, age-specific incidence, and survival for this population.

A total of 5,603 kidney, liver, or combination transplants were eligible for analysis from 1966 through 2004. The mean follow-up was 9.3 years. We identified 40 cases of colorectal adenocarcinoma. Twenty-five of these cases (62%) occurred in kidney transplant recipients, 13 after liver transplant, and two after kidney–pancreas combination. Twenty-seven patients (68%) diagnosed with cancer have died, 12 of metastatic disease. The median survival postcancer diagnosis was 2.3 years. These results were compared to the National Cancer Institute Survival, Epidemiology, and End Results (SEER) database for colon and rectal cancer. The current age-adjusted annual incidence based on year 2000 census data is 0.053% (52.9/100,000), and the extrapolated 10-year incidence is 0.27%. The 10-year incidence in the transplanted cohort is 0.71% (incidence ratio = 2.6). The 5-year survival postcancer diagnosis is 63.5% in the general population (SEER), vs. 30.7% in the transplant cohort. The SEER median age at diagnosis of colorectal adenocarcinoma is 72.0 years. Of the transplant recipients who developed cancer, the median age at diagnosis was 58.7 years (32.4 to 78.2), and 11 patients (27%) were diagnosed at or before age 50. In the U.S. population, the annual incidence of colorectal adenocarcinoma below the age of 50 is 0.0055% (5.52/100,000) and the 10-year extrapolated incidence is 0.11%. The 10-year incidence in the under-50 transplant cohort is 0.33% (incidence ratio = 3.0). In this under-50 cohort, median time from transplant to cancer diagnosis was 7.8 years.

The incidence of and 5-year survival after diagnosis of colorectal adenocarcinoma in transplant recipients is markedly different than the general population. Patients are often diagnosed at a younger age. With current screening guidelines, over 25% of at-risk patients would not be screened. We propose modifying these guidelines to allow earlier detection of colorectal cancer in this population.