A study by the MGH group reported the clinical outcomes of four patients with oligometastatic breast cancer involving the sternum who received prior multimodality therapy and then underwent PBS PT irradiation to the sternal metastasis and lymph nodes. At a median follow-up of 28 months from diagnosis, none of the patients have experienced relapse within the radiation portal or developed additional sites of metastatic disease. The authors concluded that PBSPT for oligometastatic breast cancer with isolated sternal lesions is feasible with promising outcomes.