Abstract P3-12-10: Socioeconomic status in young breast cancer patients is associated with inequalities in recurrence patterns: A population-based study in the Netherlands
Authors: van Maaren Marissa Corine 
Published: March 2022

Abstract
Background Breast cancer survival is shown to be associated with socioeconomic status (SES), which is most pronounced in young patients. In this study, we investigated how consecutive recurrent events are associated with excess mortality according to SES in young breast cancer patients. Using detailed data on all recurrences that occur between date of diagnosis of the primary tumour and last observation, we provide a unique insight in the prognosis of young breast cancer patients according to SES. Methods All female patients &lt;40 years with primary operated stage I-III breast cancer diagnosed in 2005 were selected from the Netherlands Cancer Registry. Data on all recurrences within 10 years from primary tumour diagnosis were collected directly from patient files. We analysed recurrence patterns according to SES, and estimated 10-year absolute risks of recurrence, contralateral breast cancer and mortality using cause-specific cumulative incidence functions, accounting for competing risks. Relationships between SES, recurrence patterns and excess mortality were estimated using a multivariable joint model, wherein the association between recurrent events and excess mortality (expected mortality derived from the general population) was included. Results We included 525 patients. Patients of high SES were more often diagnosed with stage II breast cancer as compared to patients of low and medium SES, who more often had stage I. In addition, patients of high SES more often had well differentiated tumours and HR+/HER2- disease as compared to low and medium SES, who more often were diagnosed with moderately or poorly differentiated tumours, HR-/HER2+ and HR-/HER2- disease. Local, regional and distant recurrence risks were higher in patients with low SES, lowest in patients with high SES. Death (n=6) and contralateral breast cancer (n=14) as first events were rare. The percentage of patients who died following a recurrence was 19.1% in low SES, compared to 15.3% and 13.2% in medium and high SES. Patients of low SES had more consecutive recurrences as compared to patients of high SES. In addition, they had shorter time intervals between diagnosis and first recurrence, and between first recurrence and death. In the joint model, adjusting for confounding, high SES was significantly related to lower 10-year recurrence rates, compared to low SES. Over the 10-year period, a strong association between the recurrence process and excess mortality was found. Conclusion This study shows that high SES is associated with a lower risk of 10-year recurrence overall, and less subsequent recurrent events, and that the pattern of recurrence is largely associated with the risk of extra mortality. Patients of low SES show a faster disease progression as compared to patients of high SES. Patients in the low socioeconomic group more often have HER-/HER2- disease, which suggests that there may be other breast cancer risk factors that play a role. Differences in treatment of recurrences were not assessed in this study and should be subject for further research, in order to further reduce socioeconomic differences.
Citation Format: Marissa Corine van Maaren. Socioeconomic status in young breast cancer patients is associated with inequalities in recurrence patterns: A population-based study in the Netherlands [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-12-10.