Breast cancer subtype of French women is not influenced by socioeconomic status: A population-based-study

Context: The molecular subtype of breast tumours plays a major role in cancer prognosis and treatment options. Triple negative tumours (TN) carry the worst prognosis and affects most frequently women of low socioeconomic status (SES). Studies have shown that non-biologic factors, such as the socioeconomic status could have an influence on tumour biology. To this date no study has been done investigating this association in French women. The objective is to study the association between the SES and the molecular tumour subtype of breast cancer patients in the French county of Côte d’Or. This study benefits from the population data from the Côte d’Or breast cancer registry known for its strict quality control policy. Methods: Invasive breast cancer cases between 2003 and 2013 were extracted from the Breast cancer registry database in Côte d’Or. A multivariate analysis was conducted using a hierarchical polytomous regression for the multinomial outcomes for the cancer subtype with HR+/HER2 as reference category. Results: A total of 4553 cases were included in our study. There was no significant association found between SES and tumour subtype in French women at diagnosis. Women older than 75 years were less likely to have a TN and HR+/HER2+ breast cancer (OR = 0.66; CI95% = [0.46–0.94] and OR = 0.51; CI95% = [0.37–0.70] respectively). Women with TN tumour subtype had significantly less lymph node invasion when compared to HR+/HER2- subtype (OR = 0.71; CI95% = [0.54–0.92]). Conclusion: No significant association was found between socioeconomic status and molecular subtype. Further studies are needed to clarify the mechanisms associated with developing each tumour subtype.