Non-breast cancer mortality after a breast cancer diagnosis: A retrospective population-based study

Abstract

6619 Background: Survivorship research after a breast cancer (BC) diagnosis has identified psychosocial, functional and comorbidity outcomes that adversely influence daily life. Little is known, however, about non-breast cancer (NBC) mortality after a BC diagnosis. Methods: This retrospective cohort study included Australian women aged 30–79 years diagnosed with BC between January 1982 and December 2004, with mortality examined from January 1993 to December 2005. The age-standardized mortality ratio (SMR) was used to compare NBC causes of death in the BC cohort and the age-matched Australian female population between January 1993 and December 2005. Results: The median follow-up time for the cohort of 159,550 Australian women diagnosed with BC was 7.04 years (range 0–24.7 years). During the follow-up period, 30,819 (19.3%) died of BC, 5,403 (3.4%) died of other cancers (OC), 18,349 (11.5%) died of non-cancer (NC) causes, while 104,979 (65.8%) were still alive at the end of the follow-up period. Excluding the first year after diagnosis, women with a prior BC diagnosis had a higher risk of mortality (SMR = 328.6.95% CI = 324.8–332.3, p < 0.001) than the age matched female population. NBC mortality risk was elevated for OC (SMR = 103.7, CI = 100.1–107.5, p = 0.022) but reduced for NC causes (SMR = 94.9, CI = 92.3–97.5, p < 0.001). For the age groupings 30–49 years (n = 46,736), 50–69 years (n = 82,967), and 70–79 years (n = 29,847), SMR's for NC causes were 168.2 (CI = 144.1–195.1, p < 0.001), 100.9 (CI = 95.9–106.1, p = 0.355), and 90.5 (CI = 87.5–93.5, p < 0.001) respectively. Following the first year of diagnosis, the SMR for OC was non-significantly elevated with time after diagnosis. In comparison, the SMR for NC causes reduced with time after diagnosis; SMR = 96.4 (CI = 92.1–100.8, p = 0.055) at 2–5 years after diagnosis, 98.2 (CI = 93.7–102.8, p = 0.222) at 6–10 years, 92.8 (CI = 87.2–98.7, p = 0.008) at 11–15 years and 82.2 (CI = 74.8–90.2, p < 0.001) at more than 15 years. Conclusions: BC survivors have a higher risk of mortality from OC compared to the aged-matched Australian female population, but a reduced risk from NC causes. Although NC mortality is lower in older women and as time from BC diagnosis increases, women less than 50 years have a higher risk of NC mortality. No significant financial relationships to disclose.