Male breast cancer (MBC) is a rare breast carcinoma subtype with limited available data to fully delineate its recurrence patterns and guide evidence-based therapeutic strategies. We report a rare case of pleural relapse in a 59-year-old male patient following a radical resection of right breast cancer. Initially diagnosed with pathological stage IIIB disease, the patient then underwent adjuvant chemotherapy, radiotherapy, and endocrine therapy. During postoperative surveillance, persistent nodular pleural thickening along the interlobar fissures of the right lung was detected. Thereafter, the patient underwent pulmonary nodule resection and systematic lymph node dissection, with electrocautery-assisted resection or excision of all visible pleural nodules, followed by an immediate platinum-based intrapleural perfusion chemotherapy. Histopathological and immunophenotypic analyses confirmed metastatic breast carcinoma. Adjuvant therapy with abemaciclib and letrozole was initiated, and no recurrence was observed during the 27-month postoperative follow-up. Taken together, our findings underscore the importance of screening for solitary pleural metastasis at initial diagnosis and during follow-up for MBC and support a potential role for palliative surgical resection in locoregional MBC recurrence to achieve durable disease control and prolonged survival, providing a feasible treatment option for carefully selected patients.

Cutaneous Metastases of Male Breast Cancer.

Male breast health and breast cancer risk.

Abstract Background: Estrogen receptor-positive (ER+) breast cancer is the most commonly diagnosed subtype in both male and female patients. However, due to the rarity of male breast cancer overall, there remains limited understanding of how this specific subtype is treated and how outcomes compare between sexes. This study aims to compare survival and contemporary treatment for ER+ male breast cancer (MBC) and female breast cancer (FBC) patients within the Veterans Health Administration (VHA). Methods: We conducted a retrospective cohort study of patients diagnosed with ER+ MBC and FBC between 2000 and 2020 using national data from the VHA Informatics and Computing Infrastructure database. Demographics, tumor characteristics, treatment (surgery, chemotherapy, radiation), and survival were compared between MBC and FBC patients. Stage 0 and IV patients were excluded from our analysis. Descriptive statistics, t-tests, and chi-square tests were used to compare the cohorts. Cox proportional hazards regression models were utilized to examine overall survival, controlling for age, race, body mass index, and grade. Results: Of the 6,336 total patients identified, 17.9% (n=1,134) were male. ER+ MBC patients were 66.0% White (n=754), 23.0% Black (n=257), and 11.0% Other/Unknown race (n=123). Most ER+ MBC patients were Non-Hispanic (n=1024, 90.0%). The average BMI of ER+ MBC patients was 30.6. ER+ MBC patients were significantly more likely to be diagnosed at an older age (69.0 vs. 57.7, p <0.001). Significantly more MBC patients were diagnosed with stage II (46.5% vs. 33.2%, p <0.001) and stage III disease (20.9% vs. 10.1%, p <0.001) than FBC. Compared to ER+ FBC patients, MBC patients had significantly higher rates of ductal histology (87.0% vs. 82.0%, p <0.001), grade 2 disease (39.0% vs 32.0%, p <0.001), and grade 3 disease (24% vs. 17.0%, p <0.001). MBC and FBC ER+ patients had similar rates of undergoing surgery (MBC: 94.0% vs. FBC: 96.0%) and chemotherapy (40.0% vs. 43.3%). Significantly more ER+ FBC patients underwent radiation therapy than MBC patients (53.0% vs. 23.0%, p <0.001). In a Cox proportional hazard model, stage I (HR 1.41, 95% CI: 1.06-1.86) and stage II (HR 2.06, 95% CI: 1.64-2.58) ER+ MBC patients had significantly higher risk-adjusted hazard of all-cause mortality when compared to FBC patients. Conclusions: Despite receiving similar surgical and chemotherapy treatments, ER+ MBC were more often diagnosed at later stages and had significantly worse risk-adjusted survival compared to ER+ FBC. These findings highlight the need for increased awareness, earlier detection, and tailored treatment strategies for ER+ MBC patients. Citation Format: A. Naaseh, J. B. Gruber, R. L. Aft, K. N. Maxwell, M. W. Schoen. Sex-based differences in hormone receptor-positive breast cancer treatment and outcomes: A Veterans Health Administration 20-year cohort study [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 PS3-08-20.

Abstract Male breast cancer (MBC) is rare and often diagnosed late due to limited awareness. This retrospective study describes the clinical presentation, histopathological profile, risk factors, and treatment in a cohort of male patients from a reference breast cancer center in Northeastern Mexico. Methods: In the period from 2015-2025, a total of 11 male patients were diagnosed with MBC. Data collected from clinical records included demographic characteristics such as age of diagnosis, as well as clinical presentation (including TNM classification), associated symptoms, histopathological findings, genetic tests, initial therapeutic approach, and relevant risk factors such as obesity, alcohol use, smoking, and family history among others using a checklist designed after an extense review of literature. (Table 1). Results: The median age of diagnosis was 56 years old. Over 80% presented with a palpable mass; 20% were incidental findings. Some patients had inflammatory signs (erythema, peau d’orange), pain (5), ulceration (1), lymphadenopathy (3), or skin retraction (1). In terms of risk factors, obesity was documented in two patients, and alcohol consumption was positive in 75% of the cohort. Active smoking and family history of prostate and breast cancer was noted in four individuals. Histologically, the predominant subtype was invasive ductal carcinoma of no special type (NST). Hormone receptor status was positive in all, with high estrogen receptor expression (ER >90%) and variable PR/HER2. Ki-67 ranged from 0-40%. TNM classification at diagnosis varied, with presentations spanning from stage IA (10%) to stage IV (10%) , although locally advanced disease (stage II and III, 20%) was common. Two patients had metastases at diagnosis (lung, bone, liver). Multigene panel testing (performed in 6 patients) revealed BRCA1 (1), BRCA2 (2), and PALB2 (1) mutations. All underwent mastectomy. Chemotherapy (7), radiotherapy (8), and hormonal therapy with tamoxifen (9) were common therapeutic approaches. One patient received paclitaxel, while another with a BRCA2 variant received treatment with olaparib. Conclusion: MBC typically presents as a palpable mass, often with inflammatory skin changes. Hormone receptor positivity and BRCA2 mutations were frequent. Modifiable risk factors like alcohol use and smoking were prevalent. Inconsistent recording of risk factors limits data comparability, underscoring the need for standardized collection tools. Furthermore, the presence of familial cancer syndrome reinforces the need for genetic testing and counseling in high risk populations. Additionally, public health efforts should promote MBC awareness, early diagnosis, and timely treatment to reduce mortality and improve outcomes. Citation Format: V. Leitzelar-Bueso, L. F. Martinez-Caudillo, M. S. Guzman-Garcia, J. E. Guzman-Garcia, D. Aguilar-Y-Mendez. Male Breast Cancer in Mexico: Experience of a reference breast cancer center in Northeastern Mexico [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 PS5-04-17.

Abstract Background: Antibody-drug conjugates (ADCs) are increasingly used in the treatment of breast cancer due to their superior efficacy compared to conventional chemotherapy. The management of male breast cancer is largely extrapolated from clinical data in females and evidence regarding the efficacy of ADCs in men remains limited. This study aimed to compare survival outcomes between male and female breast cancer patients treated with ADCs across the spectrum of human epidermal growth factor receptor 2 (HER2) expression. Methods: We included total of 2,954 (Male: 34, Female: 2,920 breast cancer samples) from patients who underwent treatment with ADCs. We excluded patients with triple-negative breast cancer status due to the rarity of this subtype in males and the worse prognosis of triple-negative breast cancer, so that the cohorts would be more homogeneous without overrepresentation of triple-negative breast cancer in females. We categorized patients by HER2 status as: HER2-null (if there was 0% stain on HER2 IHC), HER2-ultra low (if HER2 IHC was 0 but with stain 1-10%), HER2-low (if HER2 IHC was 1+ or 2+ with a negative chromogenic in situ hybridization [CISH] assay), and HER2-positive (if HER2 IHC was 3+ or 2+ with a positive CISH assay). Real-world median overall survival was derived from insurance claims and calculated from the start of first ADC with either trastuzumab deruxtecan (T-DXd) or trastuzumab emtansine (T-DM1) or sacituzumab govitecan (SG) to last contact using Kaplan-Meier. Statistical significance was assessed using chi-square and Mann-Whitney U. Results: The distribution of sex by HER2 expression group was: HER2-null: 8 males vs 612 females; HER2-ultra low 6 males vs 467 females; HER2-low 11 males vs 903 females; HER2-positive 9 males vs 938 females. Median survival from treatment initiation with either T-DXd or SG in the HER2-null cohort was 21.31 months in males vs 15.72 months in females (HR 0.82, 95% CI 0.33 - 2.01, p=0.67); in the HER2-ultra low cohort was 17.73 months in males vs 14.47 months in females (HR 0.84, 95% CI 0.26 - 2.63, p=0.76); in the HER2-low cohort was 11.08 months in males vs 18.62 months in females (HR 1.53, 95% CI 0.63 - 3.7; p=0.34). In the HER2-positive cohort, 5/9 males (55.5%) and 544/938 females (58%) were treated with T-DXd. Median survival from treatment initiation with either T-DXd or T-DM1 in the HER2-positive cohort was 36.55 months in males vs 46.52 months in females (HR 1.77, 95% CI 0.84 - 3.74, p=0.12). Conclusions: In this study, survival appears to be comparable between males and females with breast cancer across the spectrum of HER2 expression when both are treated with ADCs, although the survival in the HER2-positive cohort appears numerically lower in males, consistent with data on HER2-positive MaBC. An important limitation is the small sample size of the male breast cancer cohorts, and the lack of a categorization of HER2 in HR+ vs HR-, for the small MaBC sample size. However, to our knowledge this is the first analysis evaluating outcomes of men treated with ADCs across the spectrum of HER2 expression. Citation Format: D. Trapani, S. Deshmukh, S. Wu, J. Xiu, N. Lin, G. Curigliano, P. Spanheimer, S. Gandhi, S. Chumsri, S. Graff, M. Lustberg, G. Sledge Jr, S. Tolaney, J. Leone. Comparative efficacy of antibody drug conjugates (ADCs) in male versus female breast cancer across the spectrum of HER2 expression [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 PS4-01-13.

Abstract Objective: The objective of this study was to analyze the impact of post-mastectomy radiotherapy (PMRT) in male breast cancer (MBC) patients and develop an artificial neural network (ANN) model to identify a potential PMRT benefit population. Methods: Data from a total of 2,247 MBC patients with T1-2N0-1M0 who underwent total mastectomy between 1998 and 2016 were enrolled from the SEER database. Propensity score matching was used to reduce covariate imbalances. Cox regression analysis was conducted to compare overall survival (OS) between the PMRT and no-PMRT groups. The hypothesis was that patients who had undergone PMRT and lived longer than the median OS of the no-PMRT group could benefit from PMRT. An ANN model was then developed to predict PMRT benefit population. Results: Multivariate Cox regression analysis demonstrated better OS in the PMRT group compared to the no-PMRT group of matched patients. This survival benefit was particularly significant in patients with grade III or T2N0 and T2N1 disease, while no significant difference was observed in patients with grade I/II or T1N0 and T1N1 disease. An ANN model was established to predict PMRT benefit population based on patients with T2N0/T2N1. The optimal cut-off value for the model predicted probability was 0.51. Survival curves indicated that a score of 0.51 could accurately distinguish potential PMRT benefit population. Conclusions: For MBC patients with T2N0, T2N1, and grade III, PMRT would improve survival. The ANN model would be used to identify patients who are likely to benefit from PMRT and aid in clinical decision-making. Citation Format: K. Huang, Y. Yu, X. Li, Y. Liu, K. Huang, X. Wang, J. Zhang. The Impact of Post Mastectomy Radiotherapy(PMRT) on T1-2N0-1 Male Breast Cancer(MBC) and establishment of an artificial neural network(ANN) predicting model: Population-Based Study [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 PS1-07-25.

Abstract Background Male breast cancer (MBC) is rare, comprising approximately 1% of all breast cancer diagnoses. Due to its low incidence, treatment strategies are largely extrapolated from studies in female patients, and prospective data in men are limited. The monarchE trial, which established the benefit of Adjuvant Abemaciclib (AA) in high-risk hormone receptor-positive (HR+), HER2-negative early breast cancer (EBC), did not provide sex-specific outcomes. To our knowledge, this is the first report of real-world data on the use of AA in male breast cancer patients. Methods This case series is a subset of the CONCISE study, a retrospective, multicentre UK audit evaluating AA use across 21 centres between July 2022 and April 2025. Male patients with HR+/HER2- EBC who received AA were included. Data were collected using the Ledidi platform and analysed descriptively using Jamovi. Variables assessed included disease characteristics, systemic therapies received, abemaciclib duration, dose modifications, and adverse events (AEs). Results Of 1,026 patients in the CONCISE dataset, 13 (1.3%) were male. Median age at diagnosis was 72 years (range 28-81), and most patients (69%) were White. Staging at diagnosis included: Stage IB (n = 6), IIA (n = 1), IIB (n = 2), IIIA (n = 2), and IIIB (n = 1). All tumours were ER-positive, HER2-negative (IHC 0-2+). Tumour grade distribution: G1 (n = 1), G2 (n = 6), and G3 (n = 5).Neoadjuvant chemotherapy was administered in 2 patients; neoadjuvant endocrine therapy (tamoxifen) in 1. Breast-conserving surgery was performed in 1 case; the remainder underwent mastectomy. Adjuvant chemotherapy was delivered in 8/13 patients (62%), with 75% completing ≥6 cycles. Adjuvant ET included tamoxifen (n = 8), aromatase inhibitors with ovarian function suppression (OFS) (n = 5).Median AA duration was 12.3 months (range 1.9-24). At the time of analysis, 4 patients (31%) remained on therapy. Among those who discontinued, 5 (56%) stopped prematurely due to toxicity, 1 due to disease progression, and 3 completed the full 24-month course. At least one dose reduction occurred in 6 patients (46%), with a second reduction in 1.AEs included diarrhoea in 7 patients (54%, ≥G2 in 1), anaemia in 4 (31%, ≥G2 in 2), neutropenia in 6 (46%, ≥G2 in 5; including G3 in 3), thrombocytopenia in 3 (23%, ≥G2 in 2), and transaminitis in 2 (15%, G1 only). No treatment-related deaths were reported. Conclusion This is the first UK real-world cohort reporting on AA use in male breast cancer, an underrepresented population. Compared to the monarchE AA+ET cohort, male patients were older (median age 72 vs. 51 years), had slightly shorter treatment duration (12.3 vs. 14 months), and similar rates of dose reduction (46% vs. 41.2%). However, discontinuation due to toxicity was higher in this cohort (56% vs. 16.6%), highlighting the need of larger, prospective cohorts for tailored toxicity monitoring and management strategies in men receiving AA. While these findings should be generalised with caution due to limited sample size, treatment overall appears manageable and associated with toxicity profiles seen in other populations. Citation Format: A. Ghose, H. Abdallah, Y. Owoseni, A. Maniam, B. Baraka, S. Horne, A. Nazir, L. Mooney, F. Nazeer, N. Atsumi, L. McAvan, M. Abraham, D. Morgan, G. Langford, E. Bean, E. Morris, R. Muhammad, E. Daniels, R. Pravinkumar, S. Mohammed, S. Raza, C. Blair, R. Khan, M. Tsalic, R. Kussaibati, R. Douglas, K. Panagiotis, S. Waters, J. Smith, E. Papadimitraki, C. Michie, C. Wilson, A. Konstantis, O. Ayodele. Adjuvant Abemaciclib in Male Breast Cancer: A UK Multicentre Case Series from the CONCISE Study [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 PS3-09-13.

Abstract Background Male breast cancer (MBC) is a rare disease with limited data on potential racial differences in clinical and molecular characteristics, despite the fact that such differences are well-recognized in females. Understanding differences in the immune microenvironment and clinicogenomic features of MBC by race could inform future treatment strategies and improve health equity. This study leveraged the largest real-world (rw) cohort of MBC patients (pts) to date to characterize these features in Black/African American and White men. Methods Male pts with primary breast cancer who underwent xF or xT testing in the Tempus multi-modal database (Tempus AI, Inc., Chicago, IL) were identified using Tempus Lens. Statistical comparisons used Kruskal-Wallis and Chi-squared/Fisher’ exact tests where appropriate. Pts with xR testing (RNA) were classified into PAM50 subtypes and immune infiltration was quantified using quantiseq. Hormone receptor status was extracted from clinical documentation within 60 days of sample collection. Tumor mutational burden (TMB; mutations/megabase) and microsatellite instability were assessed by DNA sequencing. Real World overall survival (rwOS) was defined from the time of sample collection to death, last follow-up, or a study cutoff of 7 years, and was estimated using Kaplan-Meier methodology; comparisons used the log-rank test. Results The study cohort included 291 MBC pts: 128 White (44%) and 36 Black (12%). Among pts with available ethnicity, 93% were not Hispanic or Latino. Clinical subtypes were HR+, HER2- (39%), HER2+ (7.6%), triple-negative (7%) and 50% unknown or not otherwise specified. Median age at diagnosis was 63 years, and 87% of staged pts presented with stage IV disease. PAM50 subtyping identified Luminal A (62% of White and 68% of Black) and Luminal B (23% of White and 14% of Black) as the most common subtypes, with no significant racial differences in molecular subtypes (p=0.6). TMB was low (<10 mt/mB) and all tumors were microsatellite stable. AR (41%), PIK3CA (27%), TP53 (26%), ESR1(12%), TERT (11%) and GATA3 (11%) were amongst the most frequent somatic mutations found in the cohort overall, with no racial differences identified. BRCA2 was the most frequent germline mutation identified overall. PD-L1 negativity (<1% CPS) was more frequent in Black vs. White pts (71% vs. 50%, p=0.5). Notably, M2 macrophage infiltration was significantly lower in Black vs. White pts (median 4.58 vs 5.62, p=0.036); CD8+ T cell infiltration was also not statistically significantly lower in Black vs White pts (median 0.03 vs. 0.15, p=0.3). Median rwOS was numerically lower in Black vs White pts, though the difference was not statistically significant (19.1 vs 23.1 months; p=0.5). Conclusions This real world analysis of MBC pts revealed largely similar clinicogenomic profiles between Black and White pts, with the notable exceptions of significantly lower M2 macrophage infiltration and numerically lower CD8+ T cell infiltration and higher rates of PD-L1 negativity in Black pts. These immune microenvironment differences may have implications for immunotherapy response, underscoring the need for further research into the biological underpinnings and potential clinical impact of immune differences in racially diverse MBC populations. Citation Format: Y. Abdou, E. Jaeger, S. Fragkogianni, E. Williams, M. Ciampricotti, K. Reeder-Hayes, P. Spanheimer. Clinicogenomic and Immune Profiles of Male Breast Cancer by Race: Insights from a Large Real-World Cohort [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 PS2-06-28.

Abstract Objectives: Germline genetic testing is a critical component of personalized care in breast cancer, informing surveillance, treatment, and risk-reduction strategies for patients and their families. National Comprehensive Cancer Network (NCCN) recommend testing patients with early breast cancer and specific high-risk features. However, adherence to these guidelines in real-world community settings, and the role of social determinants such as insurance and geography, remains incompletely understood. Methods: We retrospectively reviewed charts of patients who were diagnosed with breast cancer at Sentara Norfolk General Hospital between June 1, 2019 to June 1, 2024. The sample included 89 patients, between 36 to 65 years old (M = 55.53), with 88 female patients and 1 male patient. Patients were deemed eligible for genetic screening in accordance NCCN Guidelines Version 1.2025, which included: 1) diagnosis of breast cancer at < 50 years old, or 2) triple-negative breast cancer, multiple primary breast cancers, or male breast cancer, or 3) a family history of one or more close blood relative with breast cancer at or before age 50, pancreatic cancer, male breast cancer, ovarian cancer, prostate cancer with high-risk features, or three or greater breast and/or prostate cancer diagnoses on the same side of the family [1]. Demographic variables included race, marital status, insurance, and social vulnerability, which was derived from zip code. Results: Genetic testing was ordered for 75% of patients (n=67). Of the total sample, 65 out of 89 patients had testing completed. Fisher’s exact tests explored relationships between social determinants and testing. For eligible patients, no significant relationships were found. However, examination of subgroup testing completion rates showed some group differences. Nearly 92% of White eligible patients received testing, compared to 77% of Black eligible patients. Married patients completed testing at a rate of almost 87%, while 70% of single people completed testing. Additionally, ninety-two percent of eligible patients with a qualifying family history were tested, compared to 83% based on age and 80% based on cancer type. Discussion: Despite high overall adherence to NCCN guidelines for germline genetic testing in this community-based breast cancer cohort, disparities emerged across several social dimensions. While statistical significance was not reached, subgroup analyses revealed meaningful trends. Black patients were less likely to complete testing compared to White patients, highlighting potential racial disparities in access, communication, or trust. Similarly, single patients had lower testing completion rates than married patients, suggesting that social support may influence engagement with genetic services. Overall, these findings suggest that even in a high-performing clinical setting, social determinants of health may influence the delivery of precision oncology, and targeted interventions are needed to ensure equitable access to genetic testing for all eligible patients.

Abstract Background: Due to the rarity of male breast cancer (MBC), prognosis prediction and chemotherapy indication remain understudied. We aimed to develop a generalized model to predict outcomes and identify candidates for chemotherapy omission in luminal early-stage MBC. Methods: Luminal MBC patients from the Surveillance, Epidemiology, and End Results (SEER) program (2010-2018, N=2996) and a Chinese cohort (2000-2020, N=599) were included. SEER-derived patients (2010-2016) were split into training (N=1356) and test (N=905) sets in a 6:4 ratio; others formed the US validation set (2017-2018, N=735). Chinese patients constituted the CHN validation set. The primary outcome was overall survival (OS). Four machine learning models and a Cox-based nomogram were evaluated. Risk stratification (low-, intermediate-, and high-risk groups) was based on the tertiles of 5-year risk scores in the training set predicted by the optimal model. Survival analysis employed Kaplan-Meier, log-rank tests, and Cox regression. Results: The optimal model showed robust performance (C-indices: training set=0.715, test set=0.713, US validation set=0.742, CHN validation set=0.748). OS of three risk groups differed significantly across all datasets (all P<0.001). Chemotherapy conferred no OS benefit in low-risk patients [Univariate: training set, hazard ratio (HR)=1.87, 95% confidence interval (CI), 1.24 to 2.80, P=0.002; other sets, P=0.176, P=0.147, P=0.864, respectively. Multivariate: training set, HR=1.80, 95% CI, 1.04 to 3.10, P=0.035; test set, P=0.211; US validation set, HR=3.24, 95% CI, 0.98 to 10.73, P=0.054; CHN validation set, P=0.449]. This tool has been deployed online for free access. Conclusions: Our model accurately predicts 5-year OS rates of American and Chinese male patients with luminal early breast cancer. Its risk stratification may aid in identifying low-risk patients who may be safe to omit chemotherapy. Citation Format: Y. Gao, M. Zhang, J. Nie, G. Ye, G. Sun, L. Ma, Z. Jiang, Y. Lin. An Online Tool to Assist Decisions on Chemotherapy for Men with Luminal Early Breast Cancer [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 PS3-10-22.

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.

Abstract Background: Male breast cancer is rare and understudied,with most treatment paradigms based on evidence from females. Existing studies suggest that men may have lower adherence to hormonal therapy, but large-scale data are limited. Hormonal therapy adherence significantly impacts outcomes in breast cancer treatment. However, differences in adherence patterns between male and female veterans remain understudied. Understanding these patterns is crucial for developing targeted interventions to improve adherence and patient outcomes. Methods: We conducted a retrospective cohort study using national data from the Veterans Health Administration (VHA) Informatics and Computing Infrastructure database. Veterans diagnosed with breast cancer and prescribed adjuvant hormone therapy (tamoxifen,anastrozole, letrozole, or exemestane) between January 1, 2005, and December 31, 2019,were included. Demographic and clinical characteristics were collected, and adherence was assessed. Multivariable logistic regression was utilized to identify factors associated with adherence, comparing male and female veterans. Results: A total of 7,155 veterans (1,139 males and 6,016 females) were analyzed. Male veterans were older at initial prescription (69.8 ± 10.0 years vs. 58.2 ± 10.7 years for females, p<0.001) and had higher adherence rates (74% vs. 65%, p<0.001). Multivariable regression indicated that adherence significantly increased with older age (Adj. OR: 1.03, 95% CI: 1.02-1.03;p<0.001) and among non-Hispanic/Latino individuals (Adj. OR: 1.39, 95% CI: 1.10-1.75;p=0.005), but decreased among Black veterans compared to White veterans (Adj. OR: 0.60,95% CI: 0.53-0.67; p<0.001), divorced/separated individuals (Adj. OR: 0.86, 95% CI: 0.75-1.00; p=0.049), widowed individuals (Adj. OR: 0.76, 95% CI: 0.60-0.95; p=0.018), and those with unknown cancer stage (Adj. OR: 0.80, 95% CI: 0.65-0.98; p=0.030). After adjustment, gender alone was not predictive of adherence (Adj. OR: 1.02, 95% CI: 0.87-1.20; p=0.771). Importantly, adherence to hormone therapy was significantly associated with reduced mortality risk (Adj. OR: 0.76, 95% CI: 0.67-0.86; p<0.001). Conclusion: Adherence to hormone therapy significantly improves survival outcomes among veterans with breast cancer. While male veterans demonstrated higher adherence rates, gender was not independently associated with adherence after adjustment. Targeted interventions addressing adherence disparities—particularly among younger, Black, divorced/widowed individuals,and patients with uncertain staging—could improve outcomes and reduce health disparities. Citation Format: S. Prasad, J. Gruber, R. Aft, A. Naaseh, M. Schoen. Comparative Adherence to Adjuvant Hormonal Therapy and Associated Mortality in Male and Female Veterans with Breast Cancer: A Nationwide Cohort Analysis [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 PS4-11-20.

Abstract Background: De novo metastatic breast cancer (MBC) presents distinct clinical challenges and accounts for a small proportion of all breast cancer cases. While extensive data exist for female patients, the characteristics and outcomes of male patients with de novo MBC remain poorly defined. Comparing clinicopathological features and prognoses between male and female patients may help improve personalized management strategies for this rare subgroup. In this study, we compared the clinicopathological features and prognoses of male and female patients diagnosed with de novo metastatic breast cancer. Method: This retrospective study utilized data from the Surveillance, Epidemiology, and End Results (SEER) database, including male and female patients diagnosed with de novo metastatic breast cancer, between 2000 and 2021. Demographic and clinicopathological variables were collected to compare baseline characteristics. Survival outcomes were assessed using Kaplan-Meier analysis, and multivariate Cox regression was performed to identify independent prognostic factors. Statistical analyses were conducted using SPSS version 30.0. Results: A total of 60,590 patients met the study criteria. Of these patients, 713 (1.2%) were male. 56.1% were under 65 years of age. Pathological subtypes were HR+/HER2- (61.2%), HR+/HER2+ (15.9%), HR-/HER2- (14.3%), and HR-/HER2+ (8.6%). All patients had de novo metastatic disease. Metastatic sites were bone (64.2%), lung (30%), distant lymph node (27%), liver (24.2%), brain (7.3%), and other (18%). At the time of diagnosis, statistically significant differences were detected in patient groups in terms of age (p<0.001), marital status (p<0.001), origin (p<0.001), race (p<0.001), histologic type (p<0.001), breast cancer subtype (p<0.001), liver metastasis (p<0.001), lung metastasis (p<0.001) 5-year survival of de novo metastatic female breast cancer patients was found to be better than male patients (31.4% vs. 25.6%, p = 0.036). Conclusions: Male breast cancer is quite rare. The clinicopathological features and metastatic spread of male and female patients at diagnosis differ. Female patients were found to have a better survival rate. Citation Format: I. Dogan, A. Azizy, I. D. Subası, I. Yıldız, A. Arican, S. Yücel, O. Dülgeroğlu, M. Bozkurt, C. Uras. Comparison of Clinicopathological Features and Prognoses in Male and Female Patients with Denovo Metastatic Breast Cancer [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 PS1-09-11.

Abstract Importance: Breast cancer is a significant public health issue in the United States, representing 32% of all cancer cases among women and accounting for 14% of cancer-related deaths. Disparities in outcomes exist, particularly among low-income populations, including higher rates of incidence, delayed diagnosis, and poorer outcomes. These disparities are also linked to socioeconomic factors like limited access to and understanding of health information (collectively known as health literacy). Individuals with low-income and lower health literacy are more likely to experience poorer cancer outcomes, including delayed diagnosis, reduced treatment adherence, and higher mortality rates. Objective: The purpose of this study was to explore the intersection of Social Determinants of Health (SDOH) and healthcare needs documented in the electronic health records (EHR) of women with breast cancer, highlighting factors such as economic stability, neighborhoods, education, food access, community context, and healthcare systems. Design/Setting: The Kaiser Family Foundation (KFF) framework categorizes SDOH and emphasizes their impact on breast cancer care. This study utilized a deductive qualitative content analysis approach to identify SDOH documented in EHR of female breast cancer patients treated at a mid-sized mid-western academic cancer center from 2017 to 2022. Participants: Records for patients with a breast cancer diagnosis who received treatment (anticancer medications or therapies, radiation, surgery), were alive, and had at least one social work note were included. Breast cancer patients 18 years of age or older were included. Male breast cancer patients were excluded as a possible confounder due to the small sample size. Patients who were deceased or in end-of-life/hospice were also excluded. We randomly selected 200 patients, intentionally oversampling racial/ethnic minority patients to ensure there was balanced representation and a diverse final sample. The sample distribution of N=200 was 65.5% White, 28.8% Black, 2.2% Asian, 0.3% Native American, Alaskan, Pacific Islander, 1.7% Hispanic, 0.7% Multiracial, and 0.8% Other. The majority of patients were of non-Hispanic ethnicity (97.8%). Most of the participants were older adults, with an average age of 65 years old. Marital status included 38% who were married, 23% who were single, and 17.5% who were widowed. Almost half never smoked (49%), nor drank (42.5%), or used illicit drugs (70.5%). Results: Findings demonstrate the interconnectedness of various SDOH and their cumulative effects on patient outcomes. Economic strain, lack of transportation, and inadequate social support emerged as critical themes influencing patient experiences. Additionally, mental health was identified as significant, underscoring the necessity for holistic approaches that address both medical and non-medical factors in breast cancer management. Conclusion/Relevance: This study emphasizes the importance of healthcare providers routinely assessing SDOH to identify at-risk patients and connect them with necessary resources. This is especially important for patients who struggle to understand health information, follow treatment plans, and actively participate in their care. By integrating SDOH evaluations into clinical practice, healthcare professionals can enhance treatment adherence, improve health outcomes, and reduce disparities in breast cancer care. Ultimately, addressing SDOH can lead to better patient experiences, improved quality of life, and more equitable healthcare delivery. Citation Format: A. A. Wells, D. Wu, W. Hsu, B. Lartey, V. Schwegmann, C. Morrison. The intersection of social determinants of health and healthcare needs among breast cancer patients: A qualitative content analysis [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 PS5-11-15.

Abstract Background: Breast cancer (BC) recurrence risk is highest within the first 5-years following initial diagnosis, making survivorship care a critical window for intervention. As survivorship rates increase, identifying modifiable lifestyle factors that may reduce recurrence risk becomes increasingly important. While the protective factors of recreational physical activity (rPA) before BC diagnosis are well-documented, the role of post-diagnosis rPA, particularly its impact on recurrence remains less explored. Objectives: This study aimed to determine 1) if high levels of post-diagnosis rPA reduce BC recurrence risk in female survivors compared to minimal rPA and 2) if adhering to the Physical Activity Guidelines for Americans (i.e., 150 minutes of moderate-intensity physical activity weekly) reduces recurrence risk. Methods: We included observational cohort studies evaluating the association between post-diagnosis rPA and recurrence risk among adult female BC survivors published up to January 2025, in any language or geographic location. Excluded studies were interventional studies, hospital/clinical studies, male BC survivors, and those under 18 years. Databases (Medline, CINAHL, Web of Science) were searched in February 2025. Two reviewers independently screened studies at all stages. Data synthesis and analysis used pooled risk estimates (RR/HRs) and 95% confidence intervals. A meta-analysis was conducted on Stata using a random-effects model to examine the effects of post-diagnosis of rPA on BC recurrence, separately for minimal vs high rPA and meeting vs not meeting recommended guidelines. Subgroup analyses explored BC subtypes, study characteristics, menopausal status, and follow-up period as potential sources of heterogeneity. Heterogeneity was assessed using Cochran’s Q test and I2 statistics. Results: Out of 2,635 studies screened, 22 passed the initial screening for full-text review, and 9 were included in the meta-analysis (9 high versus low; 5 meeting vs not meeting guidelines). The analysis included 37,787 BC survivors and 4,524 recurrences were reported. Meta-analysis showed that female BC survivors who engaged in high levels of rPA after diagnosis had a 13% lower risk of BC recurrence compared to those with minimal activity (RR=0.87, CI=0.77-0.96, I2=0.00%, n=9). However, meeting the minimum recommendations of rPA alone was not associated with a reduced risk of recurrence (RR=0.93, 95% CI=0.85-1.02, I2=0.00%, n=5). Subgroup analysis showed stronger associations in studies conducted in the Netherlands and Germany, as well as in those with rPA assessment periods greater than 5 years after diagnosis. Using the Newcastle Ottawa Scale, study quality was classified as good (n=7) or fair (n=2). Conclusion: These findings suggest that high levels of rPA postdiagnosis reduces recurrence risk by 13%. Because the current minimum recommendations may not be sufficient to reduce recurrence risk, further research is needed to determine optimal rPA recommendations and guidelines for BC survivors. Additionally, these findings emphasize the value of healthcare professionals promoting higher levels of rPA within survivorship care plans for BC survivors. Citation Format: J. Weathington, I. Lynch, B. Sukhu, T. Glatz, E. Lee. The Relationship between Post-Diagnosis Recreational Physical Activity and Breast Cancer Recurrence: A Systematic Review and Meta-Analysis [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 PS1-05-25.

Pulmonary Tumor Thrombotic Microangiopathy in a Patient With Male Breast Cancer: A Report of a Rare Case

Male breast cancer exhibits a higher mortality rate compared to female breast cancer; however, it remains under-researched in terms of its potential consequences. This study explores men’s knowledge of male breast cancer (MBC) in Ghana. Using a qualitative approach, in-depth interviews were conducted with twenty-two (22) purposively and conveniently selected participants between the ages of 18 and 70. Thematic analysis was employed to analyze participants’ knowledge of male breast cancer. The findings revealed that most participants, including community members, a male breast cancer patient and a survivor, had limited and inaccurate knowledge of female breast cancer and no awareness or knowledge of male breast cancer. Nevertheless, these knowledge gaps did not deter participants from seeking healthcare, as most expressed willingness to undergo screening for early indicators of breast cancer. The study recommends increased education and awareness about male breast cancer through targeted community outreach.

Objective To assess global, regional, and national trends in the burden of elderly male breast cancer (EMBC) from 1990 to 2021 and to evaluate projected patterns to 2040. Methods Estimates were obtained from the Global Burden of Disease 2021 study. Age-standardised incidence, mortality, and disability-adjusted life year rates (ASIR, ASMR, ASDR) were analysed across all countries and Sociodemographic Index (SDI) strata. Long-term changes were quantified using the average annual percent change derived from log-linear models. Joinpoint regression identified temporal inflection points. Age–period–cohort (APC) models characterise independent temporal effects. Mortality changes were decomposed into components attributable to population growth, ageing, and epidemiological change. Inequality was assessed using slope and concentration indexes. Attributable mortality and DALYs were evaluated for alcohol use, dietary risks, and tobacco. Future rates to 2040 were estimated using a Bayesian age–period–cohort (BAPC) model. Results Globally, EMBC incidence, mortality, and DALYs increased from 1990 to 2021, with average annual percent changes(AAPC) of 1.8 (95% CI, confidence interval, 1.63 to 1.98), 0.58 (95% CI 0.38 to 0.77), and 0.68 (95% CI 0.43 to 0.92). East Asia recorded the steepest rise in incidence, increasing from 1.65 (95% UI, uncertainty interval, 1.16 to 2.42) to 6.65 per 100000 population (95% UI 2.77 to 9.78). The middle SDI quintile showed the largest increases in all three metrics, rising from 1.62 (95% UI 1.18 to 2.09) to 4.92 per 100000 population (95% UI 2.26 to 6.81). APC analysis indicated pronounced period and cohort effects in middle and low-middle SDI settings. Decomposition identified population growth as the dominant driver of rising burden. Alcohol use and dietary risks accounted for most increases in mortality and DALYs, while tobacco contributed minimally. Cross-country inequality was modest for incidence but more marked for mortality and DALYs. Projections suggest that age-standardised rates will decline gradually by 2040, although absolute case numbers may continue to rise in rapidly ageing regions. Conclusion The global burden of EMBC continues to increase, with substantial regional and socioeconomic disparities. Although age-standardised rates are projected to decline, population ageing is expected to sustain or expand absolute numbers of cases and deaths.

Unexpectedly high information needs regarding male breast cancer: insights from a german web-based analysis