e-Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2020

Do Histopathological features of Breast Cancer in Australian Indigenous Women explain the survival disparity? A two decade long study in the Northern Territory (#226)

Sophia Frentzas 1 , David Read 2 , Linda Ward 3 , Paolo De Ieso 4 , Samantha Chen 5
  1. MEDICAL ONCOLOGY, Monash Health, CLAYTON, VIC, Australia
  2. Department of Trauma, Royal Melbourne Hospital , Melbourne, Victoria, Australia
  3. Health Research, , Menzies School of Health Research, Darwin, NT, Australia
  4. Radiation Oncology, ICON Cancer Centre, Melbourne, VIC, Australia
  5. Department of Surgery, , Northern Territory, Australia, Royal Darwin Hospital,, Darwin, NT, Australia

Aims: In the Northern Territory (NT) of Australia, Indigenous women have a lower incidence of breast cancer, but a higher mortality than non-Indigenous women. The aim of this study was to describe and compare breast cancer pathological features related to stage and biological aggression between the two groups.

 Methods: Subjects were identified by extract from the NT Cancer Registry in two separate cohorts, Cohort 1 (1991-2000) and Cohort 2 (2001-2010). Data from Cohort 1 included age, stage, tumour grade and oestrogen receptor status (ER) and treatment completion. Additional pathological variables including tumour size, Her2 status, lymphovascular invasion, and derived tumour phenotype were available for the Cohort Two. Bivariate p-values for categoric variables were calculated using Fisher’s exact tests. The Wilcoxon rank-sum test was used to compare Cohort 2. Logistic regression was used to calculate odds ratios.

Results: There were 359 (44 Indigenous) eligible women in CohortOne and 496 (100 Indigenous) for Cohort Two. In cohort One, in both cohorts, Indigenous women were more likely to present at an advanced stage, but there was no difference in ER status or tumour grade. When derived phenotypes were compared, Indigenous women were less likely to have better prognosis, luminal A tumours, and more likely to have HER2 enriched tumours.

Conclusion: This two-decade long comparison of the pathological features of breast cancer between Indigenous and Non Indigenous (NI) women of the NT has confirmed that Indigenous women not only present at a later stage than NI women but are also afflicted by poorer prognosis tumours, particularly HER2 enriched