Risk of Colorectal Cancer After Solid Organ Transplantation in the United States

Abstract

Solid organ transplant recipients have increased colorectal cancer (CRC) risk. We assessed CRC risk among transplant recipients and identified factors contributing to this association. The US transplant registry was linked to 15 population-based cancer registries (1987-2010). We compared CRC risk in recipients to the general population by using standardized incidence ratios (SIRs) and identified CRC risk factors by using Poisson regression. Based on 790 cases of CRC among 224 098 transplant recipients, the recipients had elevated CRC risk (SIR 1.12, 95% confidence interval [CI] 1.04 to 1.20). The increase was driven by an excess of proximal colon cancer (SIR 1.69, 95% CI 1.53 to 1.87), while distal colon cancer was not increased (SIR 0.93, 95% CI 0.80 to 1.07), and rectal cancer was reduced (SIR 0.64, 95% CI 0.54 to 0.76). In multivariate analyses, CRC was increased markedly in lung recipients with cystic fibrosis (incidence rate ratio [IRR] 12.3, 95% CI 6.94 to 21.9, vs. kidney recipients). Liver recipients with primary sclerosing cholangitis and inflammatory bowel disease also had elevated CRC risk (IRR 5.32, 95% CI 3.73 to 7.58). Maintenance therapy with cyclosporine and azathioprine was associated with proximal colon cancer (IRR 1.53, 95% CI 1.05 to 2.23). Incidence was not elevated in a subgroup of kidney recipients treated with tacrolimus and mycophenolate mofetil, pointing to the relevance of the identified risk factors. Transplant recipients have increased proximal colon cancer risk, likely related to underlying medical conditions (cystic fibrosis and primary sclerosing cholangitis) and specific immunosuppressive regimens.

Keywords: Discipline: organ transplantation in general; Focus: cancer / malignancy / neoplasia: risk factors; Scope: health services and outcomes research; epidemiology; translational research / science.

Figure 1. Standardized incidence ratios for colorectal cancer among transplant recipients

The figure presents standardized incidence ratios by anatomic sub-site, transplanted organ, and medical conditions leading to transplantation. The horizontal axis uses a logarithmic scale. Abbreviations: CF=cystic fibrosis; PSC=primary sclerosing cholangitis; IBD=inflammatory bowel disease; NOS=not otherwise specified.

Figure 2. Colorectal cancer risk among transplant recipients according to time since transplantation

Panel A shows standardized incidence ratios for CRC (y-axis) according to time since transplantation (x-axis). Diamond markers correspond to proximal colon cancer, square markers to distal colon cancer, and triangle markers to rectal cancer. In panel A, the dashed line at a standardized incidence ratio of 1.0 indicates risk similar to the general population.