Older Breast Cancer in Australia: Tumour Characteristics of Screened Versus Symptomatic Breast Cancers

Background: Breast cancer is the most common non-skin cancer in Australia, affecting 1 in 7 women by the age of 85. The Australian 2020 projected incidence of breast cancer in the older population, 70 years or greater, is over 6500. This is almost a third of the entire projected incidence of over 20,000. BreastScreen Australia invites women aged 50-74 years of age for biennial screening; however, a significant proportion of Australian women continue screening well beyond this. We have evaluated the tumour characteristics of older breast cancer patients - comparing symptomatic to screen detected patients. Methods: This was a retrospective study of data from the BreastSurgANZ Quality Audit (BQA) between 1 January 2001 and 31 December 2019. Female patients aged ≥ 70 at diagnosis were included only. Exclusion occurred for incompletely recorded cases. Patients were then divided based on means of detection - either screen detected (Group A) or symptomatic (Group B). Results: From 1 January 2001 to 31 December 2019, 34,258 patients were appropriately reported in the BQA. There were 11,021 in Group A and 23,237 in Group B. DCIS was more prevalent in Group A (16.83% versus 6.49%, p = <.001). T stage distribution was statistically different, with higher T stages for Group B, p = <.001. IDC sub-type distribution varied between the two groups, p = <.001. IDC Grade 3 and lymphovascular invasion were more common in Group B (p = <.001). Hormonal status was statistically different, with Group B having greater rates of TNBC and HER2+ cancers compared to Group A (12.99% versus 7.10%, p = <.001 and 4.45% versus 2.55%; respectively, p = <.001). Conclusion: This is the first BQA review of older breast cancer tumour characteristics, comparing screen to symptomatic patients. As hypothesized, screen detected cancers were smaller and earlier stage, compared to symptomatic patients. Tumour biology was statistically less favourable in Group B being higher grade, and greater rates of lymphovascular invasion, TNBC and HER2+ cancers.