FrEDRIC Astaire.

Top Line: Everyone is familiar with the notorious RTOG 0617 radiation dose-escalation trial for non-small cell lung cancer (NSCLC), where doses up to 74 Gy resulted in worse local control and even survival.
The Study: Some guess that worse dosimetry to structures such as the heart led to undercoverage of target volumes and maybe even earlier death. This slightly more modern retrospective look at 117 patients treated with definitive radiation for NSCLC aimed to determine the impact of radiation to, shall we say, a more diffuse organ system. That’s right, the totally in vogue immune system. The median prescribed dose was the now standard 60 Gy, most via intensity modulated techniques, and almost all patients received concurrent platinum-based chemo. Now, estimating dose of radiation to immune cells (deemed EDRIC) required some fancy footwork using a complicated model weighing organs differently based on estimated circulation time. We will say the footwork appeared on point, though, as higher EDRIC correlated nicely with grade 3+ lymphopenia. Indeed, multivariate analyses demonstrated significant associations between higher EDRIC and worse overall and disease-free survival. Median EDRIC was 6.1 Gy, and patients in the highest quartile of EDRIC (>7.3 Gy) had a median survival half that of those in the lowest quartile (<5.1 Gy) at 14 versus 28 months.
TBL: EDRIC may represent one of the first modifiable measures of radiation’s crucial impact on patient immune systems. | Ladbury, Int J Radiat Oncol Biol Phy 2019


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