Abstract:
The overall objective of this study was to investigate factors associated with
long-term survival in axillary node negative (ANN) breast cancer patients. Clinical
and biological factors included stage, histopathologic grade, p53 mutation, Her-2/neu
amplification, estrogen receptor status (ER), progesterone receptor status (PR) and
vascular invasion. Census derived socioeconomic (SES) indicators included median
individual and household income, proportions of university educated individuals,
housing type, "incidence" of low income and an indicator of living in an affluent
neighbourhood. The effects of these measures on breast cancer-specific survival and
competing cause survival were investigated.
A cohort study examining survival among axillary node negative (ANN) breast
cancer patients in the greater Toronto area commenced in 1 989. Patients were
followed up until death, lost-to-follow up or study termination in 2004. Data were
collected from several sources measuring patient demographics, clinical factors,
treatment, recurrence of disease and survival. Census level SES data were collected using census geo-coding of patient addresses' at the time of diagnosis. Additional
survival data were acquired from the Ontario Cancer Registry to enhance and extend
the observation period of the study. Survival patterns were examined using KaplanMeier
and life table procedures. Associations were examined using log-rank and
Wilcoxon tests of univariate significance. Multivariate survival analyses were
perfonned using Cox proportional hazards models. Analyses were stratified into less
than and greater than 5 year survival periods to observe whether known markers of
short-tenn survival were also associated with reductions in long-tenn survival among
breast cancer patients.
The 15 year survival probabilities in this cohort were: for breast cancerspecific
survival 0.88, competing causes survival 0.89 and for overall survival 0.78.
Estrogen receptor (ER) and progesterone receptor (PR) status (Hazard Ratio (HR) ERIPR-
versus ER+/PR+, 8.15,95% CI, 4.74, 14.00), p53 mutation (HR, 3.88, 95% CI,
2.00, 7.53) and Her-2 amplification (HR, 2.66, 95% CI, 1.36, 5.19) were associated
with significant reductions in short-tenn breast cancer-specific survival «5 years
following diagnosis), however, not with long-term survival in univariate analyses.
Stage, histopathologic grade and ERiPR status were the clinicallbiologieal factors that
were associated with short-term breast cancer specific survival in multivariate results.
Living in an affluent neighbourhood (top quintile of median household income
compared to the rest of the population) was associated with the largest significant
increase in long-tenn breast cancer-specific survival after adjustment for stage,
histopathologic grade and treatment (HR, 0.36, 95% CI, 0.12, 0.89).
