Dear Amy,
Thanks for your post. You might want to check out the following websites as they provide some useful information about bone health generally and information about bisphosphonates and secondary breast cancer.
1. BreastCancer.org
This is an American website that has information on breast cancer and it’s treatments including the possible effects of treatment on bone health.
2. MacMillan Cancer Support (UK)
MacMillan Cancer Support provides some brief information about bisphosphonates and secondary breast cancer which can be found here.
Hope you find some of this information useful.
Astrid