In my case (using the NHS Predict tool), I have a 9% chance of my cancer returning and dying from it in the next ten years. Blocking oestrogen reduces that risk to 6%, so it's statistically significant.
At my age, I'm well aware that I'm more likely to die from something else anyway and I'm quite keen to reduce those risks too.
I also know that blocking oestrogen increases my risk of osteoporosis. My risk for a hip fracture over 10 years is 2% with oestrogen blocked and given that I already have osteopenia, which is less than the risk of the cancer returning, but is marginal. Of course, I have no way of knowing whether I'll be one of the 2%, 3%, 6%, 9% or whatever. I'll have another bone density scan in two years. If my quality of life is reduced from blocking oestrogen, I might have to reconsider.
I'm keen to do what I can to reduce osteopenia from developing into full-blown osteoporosis. Apparently, one of the biggest determinants is your nutrition as a child, when bones are being formed. Maybe people of our generation should be grateful of the milk we were made to drink at school.