COMPETING CAUSES OF DEATH FOR PRIMARY BREAST-CANCER

Background: A patient's likelihood of dying from breast cancer or anot her cause can be assessed with competing risks analyses. Methods: Data for a cohort of 678 patients with primary invasive breast cancer accr ued from 1971 to 1990, updated to 1995, included cause of death (e.g., breast cancer vs, other cause). We investigated the effects of age, t umor size, nodal status, ER, PgR, and adjuvant therapy (hormones, chem otherapy, radiotherapy) on type of death and time to death for patient s of all ages and for those over the age of 65 years. Results: Althoug h there were no significant univariate differences in breast cancer de ath rates by age group (P = 0.94), more patients over the age of 65 ye ars died from other causes (41/207 [20%] of those older than 65 years vs. 16/471 [3%] of those younger than 65 years; P <.001). In competing risks analyses, older age was associated with non-breast cancer death , whereas larger tumor size was associated with breast cancer death. P gR was positively, and nodal status negatively, associated with surviv al, regardless of type. In the older patient group, the competing risk s analyses identified similar effects for age and tumor size; in addit ion, higher ER assay values were less likely to be associated with bre ast cancer death. Conclusions: With increased lifespan, there will be more breast cancer cases in women older than 65 years; we have shown t hat women in this group have more non-breast cancer deaths. It becomes important, then, to delineate differential effects of prognostic fact ors on competing causes of death.