Abstract PS3-05-11: Is Breast Cancer After Kidney Transplant More Common in Men?

Abstract Introduction: Within the general population, male breast cancer (BC) is exceedingly rare, with approximately one case for every 100 female cases. However, as a high-volume transplant center, we have anecdotally observed several cases of male BC following kidney transplant. Despite this, the gender-specific BC incidence in solid organ transplant remains a gap in the current literature. We therefore sought to examine the gender-specific incidence of BC among kidney transplant recipients. Methods: Retrospective analysis of data from 1987-2022 from the Scientific Registry of Transplant Recipients (SRTR) database was used to identify patients who developed BC following kidney transplant. Clinical, pathological, treatment, and follow-up data were collected. Using R statistical software program comparisons of continuous variables were based on t tests and chi squared tests were used to compare categorical variables. Measures of association were based on odds ratios from multivariable logistic regression for dichotomous outcomes. Survival analyses were conducted using Kaplan-Meier curves and proportional hazard modeling for time to event outcomes. Results: Within the study period a total of 214 patients with BC were identified, with 42 developing BC in the 1,267 post kidney transplant recipients. Among the 484 women post kidney transplant, 15 (3%) developed BC compared to 27 of 783 men (3%). The majority of BC was identified in men 27 of 42 (64%). The incidence of BC in women was 0.08 per 1,000 transplants vs. 0.09 per 1,000 transplants in men. The odds ratio for association of BC with male gender was OR=1.1. (95% CI 0.6, 2.2) with no significant difference noted.The median time to mortality among post-transplant patients with BC was 144 months (95% CI, 87, NA) compared to 198 months for patients without BC (95% CI 179, 252). This difference was not statistically significantly different on Cox Proportional Hazard modeling controlling for gender (HR=1.1, 95% CI 0.6, 2.1).Controlling for gender, patients with post-transplant tumors were nearly 3 times more likely to have died. (OR=2.9, 95% CI 2.8, 2.9). There wasn’t a statistically significant association of BC with reported post-transplant mortality when controlling gender (OR = 1.0, 95% CI 0.5, 2.0). Conclusion: We observed a three-fold increase in mortality for patients who had BC after transplant surgery, regardless of gender. Additionally, we interestingly found an unexpected shift in the gender distribution of BC cases among patients who underwent kidney transplant. Unlike the typical pattern seen in the general population, male transplant recipients exhibited a slightly higher risk of developing breast cancer compared to their female counterparts. This striking reversal of the usual gender disparity in BC represents a highly significant finding. Further investigation into the factors affecting the internal hormonal milieu in these patients may shed light on the physiologic basis of this heightened risk. Understanding the risk of BC in well-defined subsets of post-transplant populations may help guide screening approaches with hopes of lowering morbidity and mortality. Citation Format: M. Sporn, C. Marsh, A. Sharma, A. Marmer, B. Greenfield, V. Tatapudi, B. Lonze, M. Gemignani, F. Schnabel, C. DiMaggio. Is Breast Cancer After Kidney Transplant More Common in Men? abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-05-11.