How do you reason the risk and benefits of low dose vaginal estrogen to a patient on an AI for postmenopausal breast cancer that is suffering from symptomatic vaginal atrophy?   

I know that many advocate using vaginal estrogen in this situation.  Most of the studies of vaginal estrogen in this situation have been small and short and don't provide any needed info on the long term breast cancer outcome.  In addition, many experts feel that any/even small amounts of absorbed vaginal estrogen can counteract the intended effect of severe estrogen deficiency with an AI.  This makes hard to counsel patients on the risks of low dose vaginal estrogen when on an AI as they seem unknown.