Longitudinal Quality of Life in Adults with Metastatic Breast Cancer: The Impact of Between- and Within-Person Changes in Symptoms and Positive Affect

Introduction : Limited research has longitudinally assessed quality of life (QoL) among patients with metastatic breast cancer (MBC) outside of therapeutic clinical trials. This study used ecological momentary assessment (EMA) to examine QoL in daily life. Methods : Patients with MBC completed 12 EMA surveys over 4 weeks. Surveys utilized a visual analog scale (0-100) to assess global QoL, symptom severity (depression, anxiety, pain, fatigue, slowed cognitive functioning, appetite loss, nausea, gastrointestinal distress, decreased libido), and positive affect (social connection, peace, joy). Multilevel mixed-effects models analyzed the relationships between QoL and symptom severity and positive affect, when ratings differed across persons (between-person differences) and among the same person (within-person differences). We also explored longitudinal changes in QoL. Results : Participants (N=118; M =57.6 years old) were a mean of 4.3 years post-diagnosis. In mixed models adjusting for sociodemographic and health variables, between-subjects effects indicated QoL was worse among individuals who reported more depression ( p =.009), more nausea ( p =.005), and less joy ( p <.001). Within-person effects indicated individuals’ QoL was lower when they reported worse depression ( p <.001), anxiety ( p =.012), and fatigue ( p =.004), lower appetite ( p =.019), lower libido ( p =.018), and less social connectedness ( p =.001), joy ( p =.040), and peace ( p <.001) than their average ratings. Mixed models estimated QoL was worse near diagnosis ( p =.028), especially for patients who were older ( p =.005) and non-partnered ( p =.001). Conclusions : Both within-person and between-person variations in symptom severity and positive affect are associated with QoL. The relative influence of within-person variation suggests the need for adaptive, targeted intervention strategies to optimize patients’ quality of life.