Characterization of time toxicity in older patients with metastatic breast cancer

Recognizing that receiving healthcare can be time intensive and burdensome, time toxicity has been conceptualized as the time spent by patients seeking healthcare. This study investigates the association between age at diagnosis and time toxicity for patients with Metastatic Breast Cancer (MBC) and identifies major components of care that confer the greatest time toxicity. We conducted a retrospective cohort study among patients with MBC aged 67 or older using the SEER-Medicare database. We assessed time toxicity using the number of encounter days patients interacted with the healthcare system per 100 days, within the first year of starting cancer treatment. We used a Poisson model to analyze the association between age and encounter days, adjusting for clinical and sociodemographic factors. We stratified the mean encounter days for each age cohort by treatment types. The final sample included 2949 patients; 51.4% were between 70 and 79 years old, and 81.3% were white. Although unadjusted analysis showed an association between older age and more encounter days (Rate Ratio (RR) 1.12; 95% CI 1.02, 1.22), there was no significant association after adjusting for comorbidities and treatment type. Patients with more than three comorbidities had significantly higher encounter days compared to those without comorbidities [RR 1.36 (95% CI 1.26, 1.46)]. Receipt of radiotherapy [RR: 1.45 95% CI (1.37, 1.54)] was associated with more encounter days compared to not receiving radiotherapy, while receipt of bone-modifying agents was associated with fewer encounter days compared to not using Bone modifying agents [RR 0.75 (95% CI 0.70, 0.79)]. Our study identified comorbidities and cancer treatment modality, including radiotherapy, as the factors affecting time toxicity in older patients with MBC. Assessment of an individual's comorbid medical conditions and types of treatment planned are crucial to understanding age-related impacts on encounter days and to support shared decision making in older patients.