Abstract PS7-47: Real-world treatment patterns in older patients with stage I-III breast cancer: A population-based study
Authors: Batra Atul , Kong Shiying , Rigo Rodrigo , Cheung Winson Y 
Published: February 2021

Background: The number of older patients is increasing globally. However, older patients are less likely to be offered participation in clinical trials. We aimed to assess the real-world treatment patterns in older patients with breast cancer and to examine the associations of advancing age with cancer specific survival (CSS) and overall survival (OS).

Methods: Patients aged &gt; 65 years and diagnosed with stage I-III breast cancer in a large Canadian province from 2004 to 2017 were identified. Data from administrative sources were linked with the provincial cancer registry. Patients were categorized based on their age at diagnosis: old (65-74 years), older (75-84 years) and oldest (&gt; 85 years). Logistic regression analyses were performed to determine the associations of age with receipt of surgery, chemotherapy, radiotherapy, and hormone treatment. Kaplan-Meier survival curves were plotted to estimate the 5-year CSS and OS. Cox proportional hazards models were constructed to examine the associations of age with CSS and OS, adjusting for stage and treatment.

Results: A total of 10,719 older patients were eligible. The median age was 73 (interquartile range, 68-79) years and 99.2% were women. There were 6,057 (56.5%) old, 3,438 (32.1%) older, and 1,224 (11.4%) oldest patients. The oldest patients were more likely to have a higher Charlson comorbidity index (CCI) score (&lt;.001) and present with stage III disease (P&lt;.001). Further, the oldest patients were least likely to be treated with surgery (80.2% vs 98.2%, P&lt;.001), chemotherapy (0.8% vs 24.7%, P&lt;.001), radiotherapy (14.6% vs 56.8%, P&lt;.001) and hormone therapy (41.8% vs 66.8%, P&lt;.001) compared with old women with breast cancer. In multivariable logistic regression analyses, the older and oldest patients had a lower likelihood of surgery (odds ratio [OR], 0.42; 95% confidence interval [CI],0.33-0.53; P&lt;.001 and OR, 0.10; 95% CI, 0.08-0.13; P&lt;.001), chemotherapy (OR, 0.08; 95% CI, 0.06-0.09; P&lt;.001 and OR, 0.01; 95% CI, 0.01-0.02; P&lt;.001), radiotherapy (OR, 0.50; 95% CI, 0.46-0.55; P&lt;.001 and OR, 0.13; 95% CI, 0.11-0.15; P&lt;.001) and hormone treatment (OR, 0.61; 95% CI, 0.56-0.67; P&lt;.001 and OR, 0.31; 95% CI, 0.27-0.35; P&lt;.001). There were 1,504 breast cancer related deaths and 1,845 deaths due to other causes. At a median follow-up of 4.9 years, the 5-year CSS rates were 90.7%, 84.1% and 74.9% (P&lt;.001), while 5-year OS rates were 86.2%, 71.3% and 43.2% (P&lt;.001) for the old, the older and the oldest patients. After adjusting for stage and treatment, advancing age predicted for worse CSS (older; hazards ratio [HR], 1.33; 95% CI, 1.17-1.50; P&lt;.001, oldest; HR, 1.49; 95% CI, 1.26-1.76; P&lt;.001) and worse OS (older; HR, 1.82; 95% CI, 1.67-1.98; P&lt;.001, oldest; HR, 3.13; 95% CI, 2.82-3.48; P&lt;.001).

Conclusions: Although all treatment modalities were administered less frequently with advancing age, a more significant decline was noted for adjuvant therapy than surgery. The worse CSS observed in the advanced age groups suggest a potential role for cancer-directed therapy in improving outcomes. Further research should focus on the development of less toxic treatment strategies in geriatric patients with breast cancer.

Citation Format: Atul Batra, Shiying Kong, Rodrigo Rigo, Winson Y Cheung. Real-world treatment patterns in older patients with stage I-III breast cancer: A population-based study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-47.