Abstract PO2-16-11: Real-World Data of Neuroendocrine Neoplasms of Breast
Authors: Unlu Serhan , Ogbue Olisaemeka , Lewis Gloria , Haddad Abdo , Daw Hamed , Maiti Baidehi 
Published: May 2024

Abstract
Background: Primary neuroendocrine neoplasms (NEN) of breast are rare and heterogeneous. WHO has classified NENs of non-endocrine organs into three distinct categories in 2022, however real-world data on outcomes of patients with NENs of non-endocrine organs under this new classification system are still sparse. Real world experience regarding demography, clinical presentation, treatment response, and prognosis can help identify potential areas of improvement in the management of breast NEN. Methods: Here, we present our findings from patients with NEN of breast in the Cleveland Clinic Foundation between 2000 and 2023. Pathology reports were reviewed to confirm NEN of breast origin. Neuroendocrine differentiation was determined by tumor histology and immunohistochemistry (IHC). For metastatic tumors at presentation, primary organ was determined by IHC and clinical presentation. Overall survival (OS) was from date of diagnosis of NEN. Recurrence is redemonstration of tumor following curative intent therapy, and progression is increase in tumor burden. T-test and log-rank test were used in statistical analyses. Results: Total of 97 patients were identified. Of these, 79 presented with localized disease, 18 were metastatic at presentation. 88 (91%) were invasive ductal carcinoma (IDC), and 64 (81%) were local disease at presentation and rest were metastatic. Gender spread was 92:5 (F:M). Patients with ER + disease was 84/96, PR + disease was 71, and 4/93 patients had overexpression of HER2. Median age was 70 at diagnosis. 11 patients underwent neoadjuvant chemotherapy, 15 patients underwent adjuvant chemotherapy (AC), and 58/84 patients underwent hormonal adjuvant therapy. For localized disease, median recurrence free survival (RFS) was 165 months (144-NA), and recurrence rate was 8/79 (10%). Recurrence rate for local IDC was 10% (6/64). Patients with metastatic disease at presentation had a median progression free survival (PFS) of 30 months, and progression rate was 7/18 (39%). For patients with metastatic disease, median lines of palliative therapy used was 2, with median duration of first line treatment being 3.5 months, and 10 months for second line. Most common surgical procedure was mastectomy, with 37% of patients undergoing management. Median duration from diagnostic biopsy to definitive surgery was 1 month. Median follow up was 28 months. Most common hormonal adjuvant option was anastrozole (58%), most common AC regimen was docetaxel and cyclophosphamide (39%), and most common first line palliative agent was letrozole (42%). Patients who underwent AC did not reach median OS, and patients who did not receive AC had a median OS of 148 months (p=0.8). Patients with grade 3 tumors had a median OS of 58.6 months, and grade 1 and 2 had a median OS of 148.1 months (p=0.5). Discussion: Current treatment strategies for NEN of breast mirror those of non-NEN of breast with similar histology and stage based on extrapolation of data. Recurrence rate was similar between IDC and SPC. In our cohort, survival was not significantly dependent on grade and use of AC. This might be due to the number of patients included in our study, as there was a non-significant trend towards lower OS in patients with high-grade neoplasms, and further limitations from retrospective design of study. Further research towards benefit of AC in NEN of breast and prognostic value of grading is necessary to explore management options in comparison to non-NEN of the breast.

Citation Format: Serhan Unlu, Olisaemeka Ogbue, Gloria Lewis, Abdo Haddad, Hamed Daw, Baidehi Maiti. Real-World Data of Neuroendocrine Neoplasms of Breast [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-11.