Abstract PO4-01-06: HER2-positive early breast cancer (EBC): treatment, toxicities and outcomes in a retrospective cohort of elderly patients (pts)

Abstract Background: Approximately one-third of breast cancer cases are diagnosed in women aged ≥70 years, presenting a considerable challenge to offer optimal treatment options. Ensuring appropriate care involves taking into account factors such as geriatric evaluation, comorbidities, and life expectancy. However, the lack of literature focusing on the elderly population makes it difficult to choose the correct treatment approach. Methods: We conducted a retrospective analysis including all elderly pts (≥70 years) with HER2-positive EBC treated at Vall d’Hebron hospital between 2016-2022. We evaluated treatment schemes, toxicities, and outcomes. Disease-free survival and overall survival from the time of diagnosis were assessed using Kaplan-Meier estimates. Results: Among 118 pts identified, the median age of diagnosis was 79.5 years (74-85). The main comorbidities were cardiovascular (82.2%), diabetes (19.5%), pulmonary (10.2%), and kidney diseases (9.3%). Stages (s) at diagnosis were: 16.8% sI, 56% sII and 24.8% sIII. 64.8% were hormone receptor-positive, 78.4% were HER2 3+ and 15.2% 2+ (ISH amplified). Median follow up was 29.1 months (m). Neoadjuvant (NA) treatment was administered to 60.2% of pts (n=71) of which 74.6% (n=53) received chemotherapy (CT) with taxanes (Tax) only (72.5%), anthracyclines (Ac)+Tax (17.6%) and Tax+carboplatin (7.8%). AntiHER2-agents were administered in 80.3% pts (n=57) of which 89.1% received trastuzumab and pertuzumab. 23.9% of pts (n=17) received exclusively aromatase inhibitor and 2.8% (n=2) associated double blockade. Overall, 87.3% (n=103) and 80% of NA treated pts (n=57) underwent surgery, specifically mastectomy in 37.9% and 46,6% pts in the NA group achieved a pathological complete response (pCR). 38.9% pts (n=46) were treated with surgery upfront. Adjuvant treatment (A) was administered to 82.9% (n=97) of pts, with 23.7% (n=23) receiving CT; primarily Tax (82.6%), Ac+Tax (13%) and Tax+carboplatin (4.3%). AntiHER2-agents were administered in 87.6% of pts (n=85). In the overall population, median disease-free survival (mDFS) and median overall survival (mOS) were 81.1m (95% CI 68.7-not reached [NR]) and 81.1m (95% CI 77.4-NR) respectively. In the pts who underwent surgery, mDFS was 81.1m (95% CI 68.7-NR), whereas mDFS in those who did not, was 17.6m (95% CI 13.1-NA). Pts who received antiHER2-agents in the A setting showed a mDFS of 81.1m (95% CI 81.1-NR) and mOS was NR (95% CI 81.1-NR) compared to those who did not, with a mDFS of 39.7m (95% CI 25.4-NR) and mOS of 77.4m (95% CI 25.4-NR). Toxicities were reported in 78.3% of pts (n=54) receiving NA treatment and in 54.7% of pts (n=52) in the A setting of which 25.9% (n=14) and 13.4% (n=7) corresponded to grade (G) 3 respectively. Hospitalization, treatment discontinuation and dose reduction were required in 13%, 25.9% and 29.6% of pts with NA treatment and in 23.1% and 19.6% of A pts respectively with no pts requiring hospitalization. NA/A main side effects included asthenia 70.4% (nG3=2)/67.3% (nG3=2), diarrhea 64.8% (nG3=4)/19.2% (no≥G3), neuropathy 27.8% (no ≥G3)/28.8% (nG3=1), nausea/vomiting 22.2%/3.9% (no ≥G3), infusion reaction 20.4% (nG3=2)/5.9% (no ≥G3) and cardiotoxicity in 3.8% (nG3=1)/7.8% (nG3=2). Conclusions: Our study provides real world data about the use of tailored treatments to reach a balance between treatment response and tolerance in an elderly population, with low discontinuation rates, satisfactory pCR rates and long-term results in patients treated with antiHER2-agents. It is crucial to evaluate risks and benefits of treatments in frail patients. Therefore, an oncogeriatric assessment program was started in 2021 to prospectively perform dedicated research in this population. Citation Format: Alejandra Rezqallah, Diego Gómez-Puerto, Ridhi Ranchor, Laia Joval-Ramentol, Lucia Sanz, Maria Borrell, Marcelo Alvarado-Cárdenas, Antonio San-José, Clara Morales Comas, Martin Espinosa-Bravo, Manuel Altabas, Esther Zamora, Carolina Ortiz, Patricia Gómez Pardo, Isabel Pimentel, Meritxell Bellet- Ezquerra, Mafalda Oliveira, Cristina Saura, Míriam Arumí, Santiago Escrivá-de-Romaní. HER2-positive early breast cancer (EBC): treatment, toxicities and outcomes in a retrospective cohort of elderly patients (pts) [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 PO4-01-06.