Associations Between Normal Lung Density Changes and Radiation-Induced Pneumonitis after Concurrent Chemoradiotherapy for Patients with Locally Advanced Stage Lung Cancer
Wu Q, Feghali K, Ghanem A, Liu C, Ajlouni M, Movsas B, and Chetty I. Associations between normal lung density changes and radiation-induced pneumonitis after concurrent chemoradiotherapy for patients with locally advanced stage lung cancer. Med Phys 2017; 44(6):2847.
Purpose: To investigate associations between normal lung CT density changes and radiation-induced pneumonitis (RP) after concurrent chemoradiotherapy for patients with lung cancer. Methods: Forty one patients with the stage III lung cancer were originally planned and treated using the AAA dose algorithm with prescription dose, 60-66 Gy in 2 Gy fractions. Planning was performed using IMRT or 3D-CRT techniques such that dose to normal organs was within tolerance levels. Planning CT images were rigidly registered to the follow-up CT datasets at 3 months after treatment, and dose distributions were mapped accordingly. Hounsfield Unit (HU) changes were assessed in the region encompassing V20, as well as the peri-tumoral region defined by a 3 cm uniform expansion around the ITV, in the ipsilateral lung. Clinical radiation pneumonitis was graded using CTCAE v4.03 by physicians who were blinded to HU changes in lung density (12 with grade 1 RP, 4 with grade 2 RP among 41 patients). Results: Significant correlations (Fig. 1-2) were observed between lung density changes and RP grade in the region encompassing V20 (r = 0.65, p < 0.001), and the peri-tumoral region (r = 0.60, p < 0.001). No significant correlations were found between V20, or MLD (defined by either both lungs or ipsilateral lung minus PTV) and RP, or between lung density change and RP in the region defining ipsilateral lung (Fig. 3-6). Population average lung density changes in dose bins 3-60 Gy for patients with RP grades 0-2 were comparable to the findings of others. Conclusion: Correlations noted between lung density changes in the region encompassing V20 and the peri-tumoral region with radiation pneumonitis grade could potentially be useful predictors of the risk of RP after concurrent chemoradiotherapy. A larger cohort of patients is needed to confirm these findings.