2178 - Reducing the Risk of Grade 3 or Greater Radiation Pneumonitis after Radical Radiotherapy to the Lung

Y. Yan¹, J. Kang², S. Yang², C. Qian³, Y. Zhang⁴, X. Yuan³, M. Hu⁵, Y. Zhu⁶, C. Jiang², M. Hu², R. Zhao¹, and Y. Xu²; ¹Department of Radiation Oncology, Shanghai Pulmonary Hospital Affiliated to Tongji University, shanghai, China, ²Department of Radiation Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China, ³Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China, ⁴Department of Radiation Oncology, Shanghai Pulmonary Hospital affiliated to Tongji university, shanghai, China, ⁵Department of Radiation Oncology, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China, ⁶Department of Radiation Oncology, Shanghai Pulmonary Hospital Tongji University, Shanghai, China

Purpose/Objective(s): Radiation pneumonitis (RP) is one of the most common adverse response in patients with lung cancer receiving thoracic radiotherapy. Higher grade RP is more likely to lead to more mortality and poor quality of life, which could be abated by rigorous treatment consensus formulated in our institution. In this study, we aimed to verify effective meaning of the consensus of RP and explore the clinical prognostic model for grade 3 or higher RP. Materials/

Methods: We collected information of RP patients in two years and published the new consensus on the diagnosis and treatment of radiation-related pneumonitis in August 2021. All clinicians were required to diagnose and treat RP patients according to the consensus standard. In a nutshell, clinical data of patients treated with radical radiotherapy were collected from August 2020 to August 2022, and part of patients from August 2021 to August 2022 was been treated according to the consensus. Three measures were mainly taken including limited irradiated margins of the planning target volume (PTV), individualized lung dose limitation, and standardized steroid therapy. Clinical characteristics including baseline and treatment data were obtained from 693 patients, including 623 patients in the training cohort and 70 patients in the test cohort. Three models were built using different screening methods, including multivariate logistics regression (MLR), backward stepwise regression (BSR), and random forest regression (RFR), to evaluate their prognostic power. Overoptimism in the training cohorts was evaluated by four validation methods including hold-out, 10-fold, leave-one-out, and bootstrap methods, and extra data were used to evaluate the predictive performance of the model. Model calibration, Decision curve analysis (DCA), and evaluation of the nomograms for the three models were completed.
Results: The incidence of RP was significantly decreased after consensus publishment compared to before (68.80% vs. 59.56%, P<0.05), and the probability of grade 3 or higher RP also decreased from 11.97% to 6.67% (P<0.05). A model of consensus intervention, interstitial lung disease (ILD), concurrent chemoradiotherapy, standardized steroids, carbon monoxide diffusing capacity (DLCO) in the range of 60-70%, and total lung volume exceeding 5 Gy (V5) >35.2% for the radiological parameter had the best discriminative ability with an area under the curve of 0.952 (95% CI: 0.919–0.985) in the training cohort . The calibration curve showed good agreement between the predicted and actual values, and the DCA showed a positive net benefit for the final model based on the nomogram.
Conclusion: The implementation of consensus interventions for the prevention and treatment of RP accompanied with standardized use of steroids resulted in a significant decrease in the incidence of grade 3 or higher RP. Early intervention and methods for reducing the complications of high-dose steroids will be explored in future work.