Abstract PS2-04-17: Clinical and pathological characteristics of early hormone receptor-positive, HER2 negative breast cancer patients in Panama

Abstract Background: Breast cancer is the most common malignancy and a leading cause of mortality among women. In Latin America, clinical characteristics and treatment outcomes vary by region. Improving early detection and treatment has enhanced prognosis. In Panama, limited data exists, so gathering information on early hormone receptor-positive and HER2-negative breast cancer patients can help develop better treatment strategies. Methods: This retrospective study aims to describe the clinical and pathological characteristics of early hormone receptor-positive, HER2-negative breast cancer patients treated at the Instituto Oncologico Nacional between January 2017 and December 2019. Data was summarized using frequencies and percentages. We utilized Kaplan-Meier curves to analyze survival and recurrence rates. Recurrence factors were assessed through univariate analysis with the log-rank test and multivariate analysis using Cox regression. Results: We analyzed 368 patients, primarily women (98.9%, n = 365). The median age was 58 years. Most were postmenopausal (68.3%), and 55% had N0 disease. Staging showed 32.5% in stage I, 45.8% in stage II, and 21.1% in stage III. Regarding grade, 83% were grade 1 or 2, while 17% were grade 3. The median tumor size was 2.5 cm. Estrogen receptor positivity was 90%, and progesterone receptor positivity was 60%. In adjuvant treatment, 24.9% received tamoxifen, 56.8% aromatase inhibitors, and 17.6% sequential therapy.At the follow-up on May 31, 2025, 15.5% of patients had local or distant recurrence, and 10.3% had died; the median time to recurrence-free survival was not reached. Univariate analysis identified several risk factors for recurrence: premenopausal status (HR 1.76 CI 1.04-2.97; p=0.032), tumor size >2 cm (HR 2.40 CI 1.33-4.33; p=0.03), positive lymph nodes (HR 2.40 CI 1.33-4.33; p=0.03), grade 3 tumors (HR 2.08 CI 1.16-3.70; p=0.01), high nodal rate (HR 2.97 CI 1.59-5.54; p=0.001), stage III (HR 4.2), and use of aromatase inhibitors versus tamoxifen (HR 1.89). Multivariate analysis showed only stage III disease (HR 2.91 CI 2.49-7.04; p<0.001) and adjuvant tamoxifen use versus aromatase inhibitors (HR 2.27 CI 1.14-4.54; p = 0.02) were significantly associated with recurrence, while grade 3 tumors showed a trend toward significance (HR 1.84 CI 0.98-3.44; p = 0.055 ). Conclusion: Stage III, high-grade tumors, along with the use of adjuvant tamoxifen, are associated with a higher risk of recurrence. This underscores the need for strategies such as using GnRH analogs in premenopausal patients and implementing adjuvant CDK4/6 inhibitors for those at high risk within our institution. Citation Format: C. Martin, o. castillo. Clinical and pathological characteristics of early hormone receptor-positive, HER2 negative breast cancer patients in Panama [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 PS2-04-17.