Top Line: Can lumpectomy boost be delivered with a simultaneous integrated boost (SIB) technique?
The Study: Several trials are asking this question. UK IMPORT HIGH has been reported in abstract form and showed relatively similar early toxicity data among >2600 women who received 40 Gy/15 whole breast RT with either sequential boost to 56 Gy, 48 Gy SIB, or 53 Gy SIB. Although the latter arm had slightly higher breast induration. Here are initial outcomes from IMRT-MC2 (MINT), a randomized phase 3 non-inferiority trial from Germany. Over 500 women received 50.4 Gy in 28 fractions to the whole breast with either sequential boost to 66.4 Gy or SIB to 64.4 Gy. The standard arm used 3D-conformal planning while the SIB arm used various IMRT techniques. Cosmesis was assessed using the breast retraction assessment (BRA) score and patient/physician reported outcomes. There was no difference in cosmetic outcomes at 6 weeks and 2 years post-treatment. Just under 90% of patients in both arms reported good or excellent cosmesis at 2 years. There was also no difference in the expectedly high rate of local control between arms (both >99%). Obviously this trial demonstrates the safety and efficacy of an IMRT-SIB technique with conventional fractionation, but ongoing trials are evaluating SIB with hypofractionated regimens using different boost dose levels.
TBL: With conventional fractionation, a simultaneous integrated lumpectomy boost is feasible using IMRT and has comparable short-term local control and cosmetic outcomes compared to sequential boost. | Horner-Rieber, Int J Radiat Oncol Biol Phys 2020