Cause-specific mortality after a breast cancer diagnosis: a cohort study of 10,195 women in Girona and Tarragona

Abstract

Introduction: Evidence suggests an excess of long-term mortality due to cardiovascular diseases, second tumours and other causes in patients diagnosed with invasive breast cancer (BC). Our aim was to assess this risk of death in a cohort of patients diagnosed with BC in Girona and Tarragona, northeastern Spain.

Materials and methods: Using data from the cancer registries in these areas, a population-based cohort study was carried out including all the women diagnosed with BC during 1985-2004 and followed up until December 31st 2014 (N = 10,195). The standardised mortality ratios (SMRs) were calculated for causes other than BC in the cohort at 10 years (periods 1985-1994/1995-2004) and 20 years (period 1985-1994). The impact of competing causes of death in the long-term survival was evaluated through competing risk analysis.

Results: The SMRs at 10 and 20 years for all-cause mortality, except BC, were 1.21 and 1.22. The main causes of mortality showing statistically significant SMR at 10 years were other tumours (colon, lung, corpus uteri, ovary, and haematological), diabetes mellitus, diseases of the nervous system, cardiovascular diseases (after BC, the second competing cause of death among patients diagnosed > 69 years) and diseases of the kidney. Globally, the 10-year SMR was higher in the first period. After 20 years of follow-up (1985-1994 cohort), there were 48.5 excess deaths per 10,000 patient-years for causes other than BC.

Conclusions: Women who did not die from BC at 10 or 20 years after the BC diagnosis had 20% higher risk of dying from other causes than women without BC. This excess risk must be clinically considered during 20 years after the BC diagnosis.

Keywords: Breast cancer; Cause-specific mortality; Excess mortality; Second tumour; Side effects.