SLOTH-RT.

Top Line: Re-irradiation is challenging for recurrent high-grade glioma.
The Study: Here is an interesting retrospective look at patients treated with pulsed reduced-dose radiotherapy (pRDR) and bevacizumab. It’s hypothesized that tumor cells (but not normal cells) are hyper-sensitive to very low doses of radiation. Here pRDR consisted of 10 pulsed-doses of 0.2 Gy given every 3 minutes over 30 minutes to a daily total of 2 Gy with an effective dose rate of 0.0667 Gy/minute. The tumor and FLAIR abnormality with a ~1 cm margin were treated using this method to a total of 50-54 Gy. The study compares overall (OS) and progression-free survival (PFS) outcomes with similar patients treated with bevacizumab alone. There were some pretty big discrepancies in underlying patient characteristics in favor of the pRDR arm (younger age, higher KPS, and higher proportion of WHO III tumors), however those patients had progressed through more lines of prior therapy. With that—and the relatively poor expected outcomes for recurrent high-grade glioma—in mind, median OS (16 months) and PFS (12 months) were pretty encouraging with pRDR. Sadly, there was no data on actual tumor response or toxicity outcomes using the pRDR technique.
TBL: Pulsed reduced-dose radiation with bevacizumab is an intriguing technique for re-irradiating recurrent high-grade glioma.  | Bovi, Int J Radiat Oncol Biol Phys 2020

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