Background: We report a case of a metastatic breast cancer woman undergoing therapy with fulvestrant and palbociclib that was successfully treated with thoracic stereotactic ablative radiation therapy (SABR) for a hilar lymph node metastasis. Case Description: The patient began the radiation treatment in the week off of the palbociclib and reported no acute toxicity. The CT scan showed acute pneumonia 60 days after RT although the patient reported no symptomatology. In addition, the subsequent PET/TC scan performed six months after RT exhibited a complete response of the irradiated lesion. Conclusion: The use of SABR in patients undergoing cyclin inhibitors appears to be potentially effective although the association must be further studied to investigate the toxicities.