Variations in intrinsic breast cancer characteristics in screen-detected breast cancer patients aged between 45 and 69 and above the age of 70.

Background: Increasing age is a well-recognized risk factor for breast cancer. With an increase in life expectancy of women, more older patients are diagnosed with breast cancer. This study aimed to identify the variations in breast cancer attributes and mortality in different age groups in New Zealand.

Methods: This was a retrospective study of data from the Auckland Breast Cancer Register between 1 June 2000 and 28 February 2017. Patients who were diagnosed through Breast Screen were included. Group A included those aged between 45 and 69 years. Group B included individuals with an age of 70 years or above.

Results: From June 2000 to February 2017, a total of 6304 new cases of new breast cancer were diagnosed through Auckland Breast Screen, with 5788 patients in group A and 516 patients in group B. Group B was more likely to have the lower grade invasive cancers, with fewer grade 3 cancers. Oestrogen receptor positivity was more pronounced in group B, along with progesterone receptor positivity. Conversely, HER-2 receptor was less likely to be positive in group B. There was a significantly higher breast cancer-related mortality in group B (6.0% versus 2.7%). Mortality related to other causes was also much higher in group B as compared to that in group A (12.8% versus 2.5%).

Conclusion: Women aged 70 years or above generally tend to have a more favourable type of breast cancer, with a lower tumour grade, oestrogen and progesterone receptor positivity, and lower rate of HER-2 overexpression.