Hello Robin2021 and thanks for posting, 

Because it has been well researched there are quite a lot of statistics about breast cancer outcomes but unfortunately, none that I have to hand and can easily provide because the data is complex.

As well as oestrogen sensitivity, other factors such as a cancer's stage (extent) and grade (which indicates how quickly cancer cells grow) can also be used to predict how likely it is to come back (recur). There are a couple of models that have been developed that combine several of these features - one called PREDICT is often used in the NHS.  I think the best thing to do would be to ask your specialist team to tell you what your risk of recurrence is following treatment . 

With regard to developing a second primary invasive oestrogen sensitive breast cancer in the area of breast tissue remaining after the lumpectomy, I imagine this would be low and letrozole would reduce the risk, but it isn't an impossibility. I don't have a precise figure I can give you, but again do ask your team.

I don't know what lies behind the sudden increase in hot flushes at the moment - this is another thing to tell your doctors about. It could be that you are hypervigilant at the moment and so taking more notice of them than you were before, I don't think this is a direct effect of surgery but mention it in case they want to look into it.

The benefits of extending letrozole beyond 5 years most probably will depend on the risk of recurrence which is linked to features of the disease. Statistics tend to be drawn from clinical trials, but they often use complicated statistical methods and can be tricky to interpret. As an example take a look at a summary explaining the results of a trial looking at extended letrozole on the American Society for Clinical Oncology (ASCO) website at this link. 

I expect your consultant will be able to answer any questions you have about the benefits of extending letrozole when the time comes, there may even be more data about it then, but there is no harm in asking what they can tell you now.  

I hope this is of some use. Give us a ring if you want to talk anything over on 0808 800 4040, we are here weekdays 9-5. 

Best wishes,

Julia