ESTRO 2022 - Abstract Book

S1076

Abstract book

ESTRO 2022

clinicians. We aimed to summarise radiological features of CT and FDG-PET predicting LR, and to evaluate radiomics as another tool for detecting LR. Materials and Methods We searched MEDLINE, EMBASE and PubMed databases for published studies and Web of Science, Wiley Online and Science Direct databases for conference abstracts that had patient populations with NSCLC and reported post-SABR radiological features of FDG-PET or CT and radiomics from either FDG-PET or CT. Studies for inclusion were independently reviewed by two authors. Results A summary of the results found by this review can be found in the figure below. On CT, there are certain gross radiological appearances on CT that are possibly indicative of LR. However, these features were not as well supported as those dubbed as “high-risk features” (HRF). Our preference is therefore to rely more heavily on the HRFs in the detection of LR on CT with the presence of any ≥ 3 HRFs, and in particular the presence of the individual HRF of enlarging opacity ≥ 12 months post-SABR (which performed comparably in terms of sensitivity and specificity), as being highly suspicious of LR. On FDG- PET, within the first 12 months post-SABR, if the relative reduction of SUV max from baseline is less than 5%, then this lack of reduction in SUV max is suspicious for LR. The cut-offs of SUV max >5 or SUV max >4.5 with qualitative features of mass-like shape of uptake and moderate intensity being present are more reliably utilised in the period after 12 months post-SABR. We found that generally within the first 12 months post-SABR the evidence in support of strongly performing radiological features was weaker than that after the initial 12-month period. We would therefore recommend that if the identified radiological features within the first 12 months period post-SABR are relied on, then they should be used in conjunction with one another (i.e. both FDG-PET and CT modalities are used) to increase the chances of successful detection of LR. Radiomics, while possibly being useful in the problematic 12 months post-SABR period, is still a nascent area and requires further validation.

Conclusion This research has identified common features of LR compared to RILI which may aid in early and accurate detection of LR post-SABR; further research is required to validate these findings. Further directions of research include studies focusing on the first 12 months post-treatment with particular regard to validation of a cut-off of relative reduction in SUV max on FDG-PET; validation studies of HRFs on CT; time to appearance of HRFs on CT; and additional studies using radiomics.

PO-1277 Re-irradiation in NSCLC High-dose RT: Control, Survival and Toxicity. Single institution experience

J. Germain 1 , O. Prato 1 , I. Solero 1 , M. Borras 1 , A. Ciafre 1 , N. Tejedor 2 , J. Gimeno 2 , C. Francisco 1

1 Hospital Universitari i Politècnic La Fe, Radiation Oncology, Valencia, Spain; 2 Hospital Universitari i Politècnic La Fe, Radiation Oncology (Physics), Valencia, Spain Purpose or Objective Patients affected with non-small cell lung cancer (NSCLC) may present local recurrences inside the irradiated area after receiving external beam radiotherapy. Re-irradiation with High dose radiotherapy appears as a promising approach, achieving long-term control with acceptable toxicity.This is a descriptive study reviewing the clinical outcomes of patients