I too had LHS radiotherapy . As I am er+ I am taking Letrozole . I was advised of potential damage to my heart of radiotherapy - my tumour was quite deep. I think the fatigue and feeling low / anxious - and they probably interact - is a side effect of Letrozole. I walk daily for an hour and find it helps with both - though not easy some days with joint pain but seem to be able to walk thru it. It also helps me to do a gentle stretch/ balance class twice per week both for my joints and my headspace - the latter is also helped by being out and about with others. I have also been doing the YWCA Encore hydrotherapy course available in most states - not Victoria I think ? - it’s good on two levels being with a diverse group of fellow bc ladies and also the exercise program which is gentle - geared mainly to lymphodema prevention - I do not have lymphodema . It’s once a week for 8 weeks for 2 hours in a very warm swimming pool available to anyone who has ever had breast cancer and you can do up to 4 courses . I think hard as it is at times being out and about amongst people helps plus exercise plus having this forum to unload and a small group of friends who you can talk to all helps.
