Neoadjuvant Endocrine Therapy, Palbociclib, Avelumab in Estrogen Receptor Positive Breast Cancer

Avelumab (10 mg/kg) will be given intravenously on cycles 2 - 4, every 2 weeks.

"The endocrine therapy given will depend on menopausal status.~Premenopausal women will receive tamoxifen AND either Goserelin or Leuprolide:~* Tamoxifen (20mg) will be given orally daily x 4 cycles. (Other Names: Nolvadex)~* Goserelin (3.6mg) will be given subcutaneously (under the skin) on Day 1 of each cycle x 4 cycles. (Other Names: Zoladex)~* Leuprolide (3.75mg) will be given intramuscularly (in the buttock, thigh, or upper arm) on Day 1 of each cycle x 4 cycles. (Other Names: Leuprorelin, Lupron, Eligard)~Postmenopausal women will receive letrozole:~\- Letrozole (2.5mg) will be given orally daily each cycle x 4 cycles. (Other Names: Femara)"

Palbociclib (125 mg) will be given orally on days 1-21 of each cycle x 4 cycles.