How would you approach a radiation-induced angiosarcoma of the breast after mastectomy with negative margins?  

I almost always offer adjuvant RT based on high risk of locoregional recurrence. If > 10 years from RT, I consider standard fractionation to 60-66 Gy. If < 10 years from RT, I will often given BID (1.5 Gy BID to 50-60 Gy)  

Based on this research we tend to offer RT for high grade or tumor more than 5 cm or RT induced; there is no good prospective data. Based on UF series, we offer accelerated hyperfractionation 1.5 BID to 45 to 50 Gy, treating only chest wall.