Abstract P5-11-28: Management of triple-negative breast cancer in renal transplant patients: A case report and multidisciplinary approach

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Abstract Introduction: In renal transplant (ReT) patients, the incidence of breast cancer (BC) is similar to the general population, albeit with a less favorable prognosis. The literature lacks guidelines for the diagnostic and therapeutic approach to BC in ReT patients, thus recommendations are based on those for the general population. It is crucial to manage the oncological disease while preserving the function of the transplanted organ by preventing treatment toxicity and drug interactions between immunosuppressants and oncological treatments. Case Description: This report describes a 45-year-old woman who detected a painful lump in her left breast (LB), prompting further investigation. The patient underwent ReT in 2017 due to end-stage chronic kidney disease and is on immunosuppressive therapy (tacrolimus 3.5 mg daily and mycophenolate mofetil 250 mg twice daily). Her family history of cancer includes a brother diagnosed with gastric cancer at age 55.Further investigation of the LB mass revealed a suspicious nodular formation at the transition of the upper quadrants of the LB, measuring 18x14 mm and no suspicious axillary lymphadenopathy (LB BI-RADS 5). Breast MRI revealed a 50mm unilateral atypia. An ultrasound-guided core needle biopsy was performed, which showed a left breast carcinoma of no special type, grade II, estrogen receptor (ER) negative, progesterone receptor (PR) negative (both 0%), HER2 negative (0), and Ki67 60%. Contrast-free CT scan, abdominal ultrasound, and bone scintigraphy showed no suspicious secondary lesions. The patient was referred to Medical Oncology and Genetics consultations, given her young age and diagnosis of triple-negative breast cancer (TNBC) cT2N0M0.Neoadjuvant chemotherapy (NACT) based on taxanes and anthracyclines was proposed, followed by local therapy. During a nephro-oncology meeting, it was decided to conduct weekly monitoring of renal function (pre-NACT creatinine 1.82 mg/dL). The patient completed the planned NACT without dose reductions, delays or unexpected toxicities. Dose adjustments of immunosuppressants due to subtherapeutic levels were done. Post-NACT, renal function remained stable (post-NACT creatinine 1.72 mg/dL).The patient underwent a total mastectomy with sentinel lymph node biopsy due to large tumor-to-breast-size ratio. Complete pathological response (pCR) was achieved. At 12 months post-surgery, the patient remains free of disease recurrence. Discussion and Final Comments: We share a case of a ReT patient presenting a stage IIB TNBC diagnosed five years after the ReT. The patient underwent taxane-anthracycline NACT. There was renal graft function preservation and a pCR was achieved. This was facilitated by regular renal function monitoring and a multidisciplinary approach. However, nowadays, a combination of immunotherapy (IO) and chemotherapy is the standard of care. Lessons LearnedThere is a lack of literature addressing how to manage breast cancer in ReT. Breast Cancer Treatment in ReT patients can be extrapolated from the general population. A multidisciplinary approach is crucial and regular renal function monitoring is needed.Immunotherapy's role in solid organ transplant receipts is being debated. Citation Format: Alexandra Montenegro, Diana Cardoso Simão, Leonor Fernandes, Sónia Duarte Oliveira. Management of triple-negative breast cancer in renal transplant patients: A case report and multidisciplinary approach [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-11-28.

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