Most glioblastoma multiforme (GBM) failures are in-field, leading many people to push for tighter clinical target volumes closer to 1 cm or even 0.5 cm. A prospective study at Stanford took this concept a step further by treating newly-diagnosed GBM with a 0.5 cm clinical margin with no additional planning margin using standard stereotactic brain techniques. The total dose was delivered over 5 fractions to a total dose escalated from 25 Gy to 40 Gy. At a median follow-up of 15 months, only one of 27 progressions occurred outside of a minimum EQD2 of 48 Gy10 but within 2 cm of the tumor volume. An interesting side note was that patients with radiation necrosis (n=7) were less likely to have in-field progression (14% v 80%) and lived longer (median overall survival 27 v 12 months) than those without it.
TBL: IRMA confirms that fair/poor cosmesis is slightly higher when APBI is delivered using 38.5 Gy in 10 BID fractions.
- Mendoza, Pract Radiat Oncol 2023