Due to a shorter remaining life expectancy, the risk of recurrence in older patients with low risk breast cancer is often reduced and the benefit of treatments may be very limited, especially with... Show moreDue to a shorter remaining life expectancy, the risk of recurrence in older patients with low risk breast cancer is often reduced and the benefit of treatments may be very limited, especially with adjuvant treatments. In the first part of this thesis, we studied the interplay between breast cancer mortality and other-cause mortality. In the second part of this thesis, we investigated the effect of surgery and radiotherapy in subsets of the older population of patients with breast cancer in which the actual treatment effect is questionable. Show less