Purpose: The aim of this study was to investigate radiation pneumonitis and its associated risk factors in patients with non-small-cell lung cancer treated with concurrent erlotinib and thoracic radiotherapy.
Materials and methods: We conducted an analysis of patients with nonoperable stage IIIA-IV non-small-cell lung cancer who were treated with concurrent thoracic radiotherapy and erlotinib (ClinicalTrials.gov identifier: NCT00973310). The Common Terminology Criteria for Adverse Events version 3.0 grading system was applied to evaluate the incidence of radiation pneumonitis. The lung dosimetric parameters were recorded in accordance with the treatment plan, and the study endpoint was radiation pneumonitis at grade 2 or more.
Results: Among the 24 selected clinical cases, nine were identified with radiation pneumonitis of grade 2 or above (37.5%). This included four cases with grade 2 (16.7%), two cases with grade 3 (8.3%), and three cases with grade 5 (12.5%). The results showed that the planning target volume was a significant factor affecting the incidence of radiation pneumonitis. All lung dosimetric parameters exhibited statistically significant differences between patients with pneumonitis and patients without pneumonitis. The receiver operating characteristic (ROC) curve analysis showed that all lung dosimetric parameters were useful in predicting the incidence of radiation pneumonitis. In addition, the threshold values of V5, V10, V15, V20, V30, and mean lung dose were >44%, >29%, >27%, >22%, >17% and >1,027 cGy, respectively.
Conclusion: Special attention should be paid to the adverse effects of radiation pneumonitis in concurrent thoracic radiotherapy and erlotinib treatment. Lung dosimetric parameters are important predictive factors in radiation pneumonitis.
Keywords: dosimetric parameter; erlotinib; radiation pneumonitis; thoracic radiotherapy; threshold value for lung radiation.