Truebeam stx accelerator

All patients were treated with RT ± chemotherapy according to international guidelines (30 (link)). External RT was delivered using volumetric modulated arc therapy (VMAT) on a Truebeam STx accelerator (Varian®, Palo Alto, USA). The gross tumor volume (GTV) was delineated on a planning CT scan after combining the information provided by endoscopy, contrast-enhanced diagnostic CT or MRI. The dose to the GTV was 70Gy (2Gy/fraction/day, 5 sessions/week) over 7 weeks +/- concomitant systemic treatment: Cetuximab, Cisplatin or Carboplatin.

After 18–20 h, the 200 ml saturated culture was again diluted to an OD_600nm of 0.0625 and incubated in a 37°C shaker for an additional hour until it reached an exponential growth phase with an OD_600nm of 0.5. The culture was then distributed in 13 cell culture flasks (65 ml each), one per intended IR dose. A Varian True-Beam STX^® accelerator was then used to expose the cells to a continuous spectrum of X-ray photons produced by a potential accelerator of 6 MeV (Figure 1). The studied doses were set between 0 and 3,000 Gy in steps of 250 Gy, at a dose rate of 12.6 Gy per minute and with an overall estimated error of the absorbed dose of 3.6%. During the exposure, a flask was extracted per each dose, substituting it by a flask filled with water to maintain the dose homogeneity. The survival rates were then studied following the guidelines described in the Data Acquisition Analysis section. The surviving cultures were stored at –80°C.