Organ transplant recipients are at increased risk of a wide range of malignancies, especially cutaneous squamous cell carcinomas (SCC). Few previous population-based studies have quantified and compared cancer risks according to graft type and with long-term follow-up. Using nationwide Swedish registers, we identified 10,476 recipients transplanted from 1970 to 2008 and followed them for cancer occurrence. Relative risks of cancer in comparison with the general population were expressed as standardized incidence ratios (SIR) and within the transplanted cohort as incidence rate ratios (IRR). During a total follow-up of 93,432 person-years, patients were diagnosed with 1,175 cancers excluding SCC, and with 2,231 SCC, SIRcancer excl SCC 2.4 (95% CI, 2.2–2.5); SIRSCC 121 (95% CI, 116–127). Cancer risks were most increased among heart and/or lung recipients SIRcancer excl SCC 3.3 (95% CI, 2.8–4.0); SIRSCC 198 (95% CI, 174–224), followed by kidney SIRcancer excl SCC 2.3 (95% CI, 2.1–2.4); SIRSCC 121 (95% CI, 116–127) and liver recipients SIRcancer excl SCC 2.3 (95% CI, 1.9–2.8); SIRSCC 32 (95% CI, 24–42). During follow-up, risk of cancer excluding SCC remained stable while risk of SCC tripled over 20 years irrespective of graft type, partly due to a subgroup of patients developing new SCCs at a rapidly increasing rate. In summary, post-transplant cancer risk varied by transplanted organ and by cancer site, with the bulk of the excess risk driven by an exceptionally high and accelerating risk of SCC. These findings underscore the importance of regular skin screening in organ transplant recipients.What's new?
After an organ transplant, the immune system must be permanently suppressed, to allow the foreign organ to survive in the body. With the immune system stifled, viruses that cause cancer have a much easier time of it, and transplant recipients are known to have increased cancer risk. The present study examined more than 10,000 organ transplant recipients over a 20-year period to determine their risk of various cancers, including skin cancer, which had not been included in previous studies. They found that the risk of squamous cell carcinoma shot up 100-fold overall, while the risk of other cancers doubled. These detailed estimates of risk over time will greatly assist doctors working with these transplant patients.