2493 - Prospective Validation of a Pretreatment 18F FDG PET CT plus Mean Lung Dose Model to Predict Early Radiation Pneumonitis in Locally Advanced Non-Small Cell Lung Cancer Patients Treated with Chemoradiation and Consolidation Immunotherapy
Presenter(s)
A. Apte1, M. Thor1, M. Grkovski1, C. B. Simone II2, D. Gelblum3, P. Iyengar3, A. J. Wu3, J. Y. Shin3, T. L. Chaunzwa3, J. Ma4, D. Billing3, M. Dunphy5, J. Chaft6, D. R. Gomez3, J. O. Deasy1, and N. Shaverdian3; 1Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, 2New York Proton Center, New York, NY, 3Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 4Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 5Memorial Sloan Kettering Cancer Center, NEW YORK, NY, 6Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s): Early radiation pneumonitis (RPEarly), i.e., RP developing within 3 months from completed concurrent chemoradiation (cCRT), leads to morbidity, necessitating the discontinuation of consolidation immunotherapy, which thereby leads to poor survival in patients with locally advanced non-small cell lung cancer (LA-NSCLC) treated with cCRT and consolidation immunotherapy. The purpose of this work was to assess the validity of a previously published model for predicting risk of RPEarly that utilizes pre-treatment 18F-FDG PET/CT imaging of the normal lung and the mean lung dose (MLD) in an independent cohort.
Materials/Methods: The 90th percentile of the standardized uptake value (SUVP90) of the normal lungs in the pretreatment 18F-FDG PET/CT images and the MLD (converted to EQD23) were calculated in 50 LA-NSCLC patients consecutively treated with cCRT and consolidation immunotherapy. For these 50 patients, the SUVP90 and MLD logistic regression coefficients assessed from the previous derivation cohort (N=160) were applied, and the model performance was evaluated using the area under the receiver-operating characteristic curve (AUC) p-values, and the Hosmer-Lemeshow test (pHL). In addition, the model was refitted to the new validation cohort.
Results: Seven of the 50 patients (14%) developed RPEarly. The performance of the previously developed SUVP90 and MLD model improved with re-fitting (AUC=0.76 vs. 0.72; p=0.01 vs. 0.10; pHL=0.66 vs. 0.94). Combining the derivation and validation cohorts (N=210) generated predicted RPEarly-stratified risk tertiles refitted to the combined cohorts (Table).
Conclusion: The previously developed SUVP90 and MLD risk model for RPEarly indicated a high probability of correctly predicting RPEarly in this prospective validation cohort. This further improved by refitting model coefficients. The associated pretreatment guidelines capturing this model, thus, provide quantitative, patient-specific RPEarly risk estimates, which could further improve identification of patients at increased RPEarly risk and guide MLD mitigation strategies during treatment planning.
Abstract 2493 - Table 1| Table. Mean (SD) | Low Risk | Intermediate Risk | High risk |
| Predicted RPEarly Risk [%] | 5 (2) | 10 (2) | 23 (11) |
| SUVP90 | 0.9 (0.2) | 1.0 (0.2) | 1.3 (0.4) |
| MLD [Gy] | 7.4 (2.3) | 11 (1.7) | 14 (2.1) |