How would you approach systemic treatment of oligometastatic recurrence following surgical removal of the single area of metastasis in a patient with ER+ (20-30%), PR-negative, HER2-negative breast cancer?  

I would most likely start the patient on endocrine therapy and a CDK4/6 inhibitor. Even though the response rate is lower with this approach in patients with lower hormone receptor-positive breast cancer, it can still be a reasonable option, and it would avoid chemotherapy-related risks and toxiciti...