Sex differences in cancer incidence among solid organ transplant recipients.

Background: Males have 2-3-fold greater risk of cancer than females at most shared anatomic sites, possibly reflecting enhanced immune surveillance against cancer in females. We examined whether these sex differences remained among immunocompromised adults.

Methods: Using the Transplant Cancer Match (TCM) study, we estimated the male-to-female incidence rate ratio in TCM (M:F IRRTransplant) for 15 cancer sites diagnosed between 1995 and 2017 using Poisson regression. Male to female IRRs in the general population (M:F IRRGP) were calculated using expected cancer counts from the Surveillance, Epidemiology, and End Results Program, standardized to the transplant population on age, race and ethnicity, and diagnosis year. Male to female IRRs were compared using a chi-square test.

Results: Among 343 802 solid organ transplants, 211 206 (61.4%) were among men and 132 596 (38.6%) among women. An excess cancer incidence in males was seen in transplant recipients, but the sex difference was attenuated for cancers of the lip (M:F IRRTransplant: 1.81 vs M:F IRRGP: 3.96; P < .0001), stomach (1.51 vs 2.09; P = .002), colorectum (0.98 vs 1.43; P < .0001), liver (2.39 vs 3.44; P = .002), kidney (1.67 vs 2.24; P < .0001), bladder (2.02 vs 4.19; P < .0001), Kaposi sarcoma (1.79 vs 3.26; P = .0009), and non-Hodgkin lymphoma (1.34 vs 1.64; P < .0001). The M:F IRRTransplant was not statistically different from the M:F IRRGP for other cancer sites.

Conclusions: Although male solid organ transplant recipients have higher cancer incidence than female recipients, the attenuation in the male to female ratio for many cancers studied relative to the general population might suggest the importance of immunosurveillance, with some loss of advantage in female recipients due to immunosuppression after transplantation.