Abstract PO1-02-14: Breast cancer in older women - long-term prognosis by age and subtype in a large population-based cohort
Authors: Chiorescu Amelia , Johansson Anna L V , Valachis Antonis , Matikas Alexios , Frisell Jan , Holmberg Lars , Fredriksson Irma 
Published: May 2024

Background Compared to middle-aged women, older women have a higher risk of breast cancer death. Whether the increased risk of breast cancer death is present in all subgroups of older adults with breast cancer, or negligible in the subgroups receiving adequate surgical and oncological treatment, has been debated. We studied long-term prognosis by age and subtype, adjusting for stage, treatment, socioeconomic status and comorbidity, clarifying which subgroups of older patients that are at increased risk of breast cancer death. Methods In a nation-wide cohort of 45,949 women aged ≥60 years at diagnosis of breast cancer 1997-2014, we estimated crude probabilities of breast cancer death and from other causes using competing risk methods. Cox proportional hazards models were used to estimate adjusted hazard ratios (HR) with 95% confidence intervals (CI. Results In this large population-based cohort study of older women with breast cancer, we found an increasing risk of breast cancer death with increasing age at diagnosis, both at 5- and 10-year follow up. The strong association between age and breast cancer death was found for all breast cancer subtypes, being most prominent in Her2-positive breast cancer. The age effect was also significant in Luminal A breast cancer where treatment opportunities are not necessarily affected by age. High-risk tumors were equally common in all age groups above 60 years. In multivariable analysis, stage, subtype, grade and treatment were important explanatory variables to the age-related differences in survival, while comorbidity and socioeconomic status contributed minorly. After adjustments, older age remained an independent risk factor for both overall and breast cancer survival. Older women with triple-negative (60-79 years) or Her2-positive (60-84 years) tumors had a 5-year risk of breast cancer death exceeding the risk of death by other causes. Conclusions Older women had a significantly higher risk of breast cancer death irrespective of breast cancer subtype, also in Luminal A disease where treatment opportunities are not necessarily affected by age.

Table 3. Crude probabilities of breast cancer specific death and death by other cause (competing cause of death) at 5, 10 and 15 years.

Table 4. Multivariable analysis of prognostic factors affecting 15-year overall (OS) and breast cancer- specific survival (BCSS)

Table 5. Multivariable analysis of prognostic factors affecting 15-year overall (OS) and breast cancer- specific survival (BCSS) by age at diagnosis and subtype.

Citation Format: Amelia Chiorescu, Anna L V Johansson, Antonis Valachis, Alexios Matikas, Jan Frisell, Lars Holmberg, Irma Fredriksson. Breast cancer in older women - long-term prognosis by age and subtype in a large population-based cohort [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 PO1-02-14.