Is there any data to quote possible benefit of endocrine therapy in an elderly woman with low risk breast cancer who is refusing primary surgical treatment?  

Yes, there are primary neoadjuvant endocrine trial versus surgery in Cochrane review (Morgan et al., Surgery versus primary endocrine for operable primary breast cancer in elderly women (70 years old); Cochrane Database Syst Rev 2014;5:1-40). The randomized trials used tamoxifen. The bottom line is ...