ESTRO 2023 - Abstract Book

S114

Saturday 13 May

ESTRO 2023

Among 451 included patients, 164 (36%) experienced severe RIL. Higher age, cN3-stage (vs. cN0-2 stage), larger planning target volume (PTV), >30 (vs. ≤ 30) RT fractions, higher mean lung dose (MLD), and lower baseline ALC were independently predictive for severe RIL in the final model. The discriminatory model performance was fair with a corrected c-statistic (after internal validation) of 0.70 (95%CI: 0.65-0.75). Model calibration among risk quintiles was excellent with mean predicted risks of severe RIL of 15%, 26%, 35%, 45%, and 62%, corresponding to observed risks of 13%, 26%, 37%, 43%, and 63%, respectively. A nomogram was created with a sum score ranging from 0 to 40 (Fig. 1). Among 169 patients with a nomogram sum score <20, adjuvant durvalumab was administered in 68 (40%). In these patients with a low predicted risk of severe RIL, durvalumab (vs. no durvalumab) yielded a significantly improved PFS (Fig. 2A; p=0.006) and OS (Fig. 2C; p=0.001). In contrast, among the 282 patients with a high predicted risk of severe RIL (nomogram sum score ≥ 20), adjuvant durvalumab in 49 patients (17%) demonstrated no superiority in terms of PFS (Fig. 2B; p=0.942) or OS (Fig. 2D; p=0.362). Fig. 1

Fig. 2

Conclusion A pretreatment model to predict severe RIL during CRT for NSCLC was developed and validated internally. Adjuvant durvalumab benefit was observed in patients with a low predicted risk of severe RIL, but not in patients with a high predicted risk. Therefore, this prediction model has the potential to enable accurate selection of high-risk patients who may benefit from lymphopenia-mitigating strategies to improve immunotherapy efficacy and survival. PD-0153 Radiation induced lymphopenia, its effect on pathologic regression and prognosis in LA lung cancer S. Appel 1 , J. Bar 2 , Y.R. Lawrence 1 , D. Urban 2 , Z. Symon 1 , J. Goldstein 3 , S. Felder 1 1 Sheba Medical Center, Radiation Oncology, Ramat Gan, Israel; 2 Sheba Medical Center, Oncology, Ramat Gan, Israel; 3 Sourasky Medical Center, Radiation Oncology, Tel Aviv, Israel Purpose or Objective Previous studies associated lymphopenia following neo-adjuvant chemoradiation (n-CRT) with adverse outcomes. We hypothesized that lymphopenia following n-CRT and surgery will correlate with decreased tumor regression and poor prognosis in locally advanced non-small cell lung cancer (LA-NSCLC). Materials and Methods Patient characteristics, treatment variables and lymphocyte nadir were extracted for analysis from an IRB approved database of patients with LA-NSCLC treated with n-CRT followed by surgery. Lymphopenia, graded according to CTCAEv5, was analyzed as continuous and categoric variables (grade 0-2 vs. grade 3-4). Primary endpoints based on surgical specimens were major pathologic regression (MPR), pathologic complete response (pCR), and mean residual tumor cells (MRTC).