Abstract PS13-08: Chemotherapy in geriatric patients with early stage HER2+ breast cancer: A National Cancer Database analysis

Abstract Background Breast cancer (BC) incidence increases with age and women ≥ 65 years account for almost half of BC related mortality. Life expectancy has increased in the US due to improvements in medical care, and therefore the number of older patients with a BC diagnosis is also expected to increase. The population of individuals ≥ 80 years in the US is growing and now comprises more than 9 million. Approximately 15% of BC are human epidermal growth factor receptor 2 amplified (HER2+). The combination of chemotherapy with trastuzumab +/- pertuzumab compared with trastuzumab alone has been shown to be cost-effective in patients 70 years and older but trastuzumab monotherapy could be considered as an option in certain patients. Nevertheless, there is limited guidelines on how to properly care for the geriatric population with HER2+ BC. Methods We conducted a retrospective analysis of data collected from the National Cancer Database (NCDB). NCDB is a joint project of the Commission on Cancer of the American College of Surgeons and the American Cancer Society. Women ≥65 years with stage I, II and III HER2+ BC were included in the analysis. Patients were categorized into three treatment groups – those who did not receive chemotherapy or monoclonal antibodies (no-CT/mAbs), those who received chemotherapy in combination with monoclonal antibodies (CT/mAbs) and those who received monoclonal antibodies alone (mAbs). Using the Logrank P value, we explored the age cut off for which survival rates were not significantly different between treatment groups. Two comparisons were done: no-CT/mAbs vs CT/mAbs and CT/mAbs vs mAbs. The main outcome of this study was all-cause mortality. RESULTS: For the first comparison, a total of 9,924 HER2+ early-stage BC patients were included. Of these, 3,052 (30.8%) received no-CT/mAbs, while 6,872 (69.2%) received CT/mAbs. Kaplan Meier curves comparing mortality by treatment in the whole sample showed that those in the CT/mAbs group had significantly improved survival, compared to the no-CT/mAbs group (Logrank P 0.001). The 1-year and 3-year survival rates were significantly higher in the CT/mAbs, compared to no-CT/mAbs. Cox proportional regression analysis showed that in the whole sample all-cause mortality was significantly lower among patients in the CT/mAbs group, compared to those in the no-CT/mAbs group (hazard ratio HR, 0.48; CI: 0.41-0.57). However, the Logrank P values showed that there was no age cut off over which CT/mAbs did not improve survival compared to No-CT/mAbs. For the second comparison, a total of 7,457 patients were included. Of these 6,872 (92.2%) receive CT/mAbs and 585 (7.8%) received mAbs. The 1-year and 3-year survival rates were significantly higher in the CT/mAbs compared to the mAbs. The Logrank P values showed that there was no age cut off over which CT/mAbs did not improve survival compared to mAbs. Conclusion Chemotherapy in combination with HER2 directed monoclonal antibodies showed a survival benefit in elderly patients, irrespective of age, when compared to no-CT/mAb and mAb alone. These data highlight the importance of individualizing treatment recommendations and not forgoing standard therapy based merely on age. Limitations of the analysis include lack of available information on BC specific mortality. Also, the benefit that we identified could be secondary to selection bias. Additional studies are needed to improve the treatment in elderly patients with HER2+ BC. Table 1. Logrank P values for survival comparison between those who received CT/mAbs and No-CT/mAbs by age cut-off. Citation Format: Ana Sandoval-Leon, Yolcar Chamorro, Muni Rubens, Mukesh Roy, Lauren Carcas, Naomi Dempsey, Manmeet Ahluwalia, Reshma Mahtani. Chemotherapy in geriatric patients with early stage HER2+ breast cancer: A National Cancer Database analysis 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 PS13-08.