Magnitude and Temporal Variations of Socioeconomic Inequalities in the Quality of Life after Early Breast Cancer: Results from the Multicentric French CANTO Cohort

PURPOSE:Socioeconomic status (SES) influences the survival outcomes of patients with early breast cancer (EBC). However, limited research investigates social inequalities in their quality of life (QoL). This study examines the socioeconomic inequalities in QoL after an EBC diagnosis and their time trends. PATIENTS AND METHODS:We used data from the French prospective multicentric CANTO cohort (ClinicalTrials.gov identifier: NCT01993498), including women with EBC enrolled between 2012 and 2018. QoL was assessed using the European Organisation for Research and Treatment of Cancer QoL Core 30 questionnaire (QLQ-C30). summary score at diagnosis and 1 and 2 years postdiagnosis. We considered three indicators of SES separately: self-reported financial difficulties, household income, and educational level. We first analyzed the trajectories of the QLQ-C30 summary score by SES group. Then, social inequalities in QLQ-C30 summary score and their time trends were quantified using the regression-based slope index of inequality (SII), representing the absolute change in the outcome along socioeconomic gradient extremes. The analyses were adjusted for age at diagnosis, Charlson Comorbidity Index, disease stage, and type of local and systemic treatment. RESULTS:Among the 5,915 included patients with data on QoL at diagnosis and at the 2-year follow-up, social inequalities in QLQ-C30 summary score at baseline were statistically significant for all SES indicators (SIIfinancial difficulties = -7.6 [-8.9; -6.2], SIIincome = -4.0 [-5.2; -2.8]), SIIeducation = -1.9 [-3.1; -0.7]). These inequalities significantly increased (interaction P < .05) in year 1 and year 2 postdiagnosis, irrespective of prediagnosis health, tumor characteristics, and treatment. Similar results were observed in subgroups defined by menopausal status and type of adjuvant systemic treatment. CONCLUSION:The magnitude of preexisting inequalities in QoL increased over time after EBC diagnosis, emphasizing the importance of considering social determinants of health during comprehensive cancer care planning.