Top Line: Is it safe to use a simultaneous or concurrent boost for whole breast radiation?
The Study: Giving a boost to the lumpectomy cavity after whole breast radiation significantly reduces local recurrence risk. The boost is typically given sequentially, but RTOG 1005 asked if the lumpectomy cavity boost could be given with a simultaneous or concurrent boost technique. The trial enrolled 2255 patients with stage I-II breast cancer who had breast conservation surgery and were planned to receive WBRT plus a boost due to the presence of high risk features. High risk features included age <50 years, positive nodes, LVI, two or more close (≤2 mm) margins, one close margin with an extensive intraductal component, focally positive margin, ER/PR-, grade 3, Oncotype >25, prior neoadjuvant systemic therapy, grade 3 DCIS in a patient younger than 50 years. Whew. They were randomized to receive standard WBRT (50 Gy/25 or 42.7/16) with a 12Gy/6 or 14Gy/7 sequential boost or WBRT with concurrent boost. In the concurrent arm, the whole breast received 40.05 Gy in 15 fractions while the boost volume received 48 Gy in the same 15 fractions. The boost target in both arms was a 1 cm CTV margin from the cavity and a 7 mm PTV margin. IMRT and 3D conformal were both allowed, and most were treated with 3D, however IMRT was used in a higher proportion in the SIB arm (24% v 14%). At 7 years, ipsilateral breast tumor recurrence was deemed noninferior with the concurrent approach (2.6% v 2.2%). There were no differences in any disease related or survival outcomes at 5 years and 7 years. Most adverse events were grade 1-2 (>70%), and there was no difference in the rate of grade 3+ events between arms. The rates of excellent or good cosmesis were similar between concurrent and sequential boost (94.9% v 96%).
TBL: In RTOG 1005, a concurrent boost of 48 Gy in 15 fractions resulted in noninferior ipsilateral breast tumor control, similar adverse effects, and similar cosmesis compared with the standard sequential boost technique. | Vincini, J Clin Oncol 2026
The Study: Giving a boost to the lumpectomy cavity after whole breast radiation significantly reduces local recurrence risk. The boost is typically given sequentially, but RTOG 1005 asked if the lumpectomy cavity boost could be given with a simultaneous or concurrent boost technique. The trial enrolled 2255 patients with stage I-II breast cancer who had breast conservation surgery and were planned to receive WBRT plus a boost due to the presence of high risk features. High risk features included age <50 years, positive nodes, LVI, two or more close (≤2 mm) margins, one close margin with an extensive intraductal component, focally positive margin, ER/PR-, grade 3, Oncotype >25, prior neoadjuvant systemic therapy, grade 3 DCIS in a patient younger than 50 years. Whew. They were randomized to receive standard WBRT (50 Gy/25 or 42.7/16) with a 12Gy/6 or 14Gy/7 sequential boost or WBRT with concurrent boost. In the concurrent arm, the whole breast received 40.05 Gy in 15 fractions while the boost volume received 48 Gy in the same 15 fractions. The boost target in both arms was a 1 cm CTV margin from the cavity and a 7 mm PTV margin. IMRT and 3D conformal were both allowed, and most were treated with 3D, however IMRT was used in a higher proportion in the SIB arm (24% v 14%). At 7 years, ipsilateral breast tumor recurrence was deemed noninferior with the concurrent approach (2.6% v 2.2%). There were no differences in any disease related or survival outcomes at 5 years and 7 years. Most adverse events were grade 1-2 (>70%), and there was no difference in the rate of grade 3+ events between arms. The rates of excellent or good cosmesis were similar between concurrent and sequential boost (94.9% v 96%).
TBL: In RTOG 1005, a concurrent boost of 48 Gy in 15 fractions resulted in noninferior ipsilateral breast tumor control, similar adverse effects, and similar cosmesis compared with the standard sequential boost technique. | Vincini, J Clin Oncol 2026