ESTRO 2022 - Abstract Book

S602

Abstract book

ESTRO 2022

Conclusion The observed increase in Δ Dose and Δ NTCP, and more efficient treatment delivery over time indicates that a learning curve was present after the introduction of IMPT. Awareness of the learning curve is important in further optimizing treatment. This may have implications for the initiation of clinical studies while still on the steep part of the learning curve.

PD-0668 Hypo- vs. standard fractionated radiotherapy in inoperable NSCLC not candidate for chemo-radiation

O. Hansen 1,2,3 , T. Schytte 1 , L.H. Land 1 , T.B. Nielsen 4 , M. Nielsen 4

1 Odense University Hospital, Oncology, Odense, Denmark; 2 University of Southern Denmark, Institute of Clinical Research, Odense, Denmark; 3 Odense University Hospital, Academy of Geriatric Research, Odense , Denmark; 4 Odense University Hospital, Laboratory of Radiophysics, Odense, Denmark Purpose or Objective The standard of radiation therapy (RT) for patients with inoperable NSCLC not candidate for SBRT or chemo-radiation is fractionated RT without chemotherapy. An alternative may be hypofractionated RT. In a retrospective study, survival after hypo-fractionated RT regimen of 45 Gy/10 fractions (F) in 2.5 weeks was compared to a standard regimen of 66 Gy/30F in 6 weeks for patients treated 2014-2020 Materials and Methods Included were 45 patients with 45Gy/10F and 113 with 66Gy/30F in performance status (PS) 0-3 with unilateral or mediastinal tumors, no distant metastases at the time of radiation. Data on date of treatment, radiation dose and fractionation, site, and the gross tumor volume (GTV), age, gender, date of diagnosis, histology, tumor stage, white blood count (WBC) at time of radiation, performance status, a modified Charlson comorbidity index (CCI), body mass index (BMI), time span since diagnosis, and the date of death was recorded. Multivariable Cox proportional hazard analyses (COX) were performed for overall survival (OS) including factors with p <0.20 in univariate analyses. Some factors were dichotomized in the analyses: PS <2/ ≥ 2, Age 0.2 in univariate analyses were gender, histology, and N-stage. PS and Age were significant factors p <.02 and both were correlated with radiation dose. The analyses were therefore stratified PS <2/ ≥ 2 and age<70/ ≥ 70. In COX, time span since diagnosis, smoking habit, WBC, and BMI were insignificant factors with p>.10. The final model included log GTV (p=.003), CCI ≥ 4 (p=.034, HR=1.6). Radiation dose was not significant (p=.56)