Ipsilateral lung dose volume parameters predict radiation pneumonitis in addition to classical dose volume parameters in locally advanced NSCLC treated with combined modality therapy

Purpose: The purpose was to determine the correlation of clinical factors and lung dose volume parameters with significant radiation pneumonitis (RP) in non-small cell lung cancer patients treated with combined modality therapy. Materials and Methods: Between January 2008 and December 2010, 52 patients of non-small cell lung cancer were treated with combined modality therapy with radical intent. Radiation pneumonitis was correlated with ipsilateral (V 20 ipsi, V 5 ipsi and MLD ipsi) and whole lung (V 20 , V 5 , and MLD) dose volume parameters. Clinical factors like pulmonary function tests (PFT), site of tumor, planning target volume, and type of treatment were also correlated with incidence of significant pneumonitis. Results: Out of 52 patients, 35.3% developed grade 2 or more pneumonitis. On univariate analysis, factors significantly correlating with radiation pneumonitis were V 5 (P = 0.002), V 5 ipsi (P = 0.000), V 20 (P = 0.019), V 20 ipsi (P = 0.004), MLD (P = 0.008) and MLD ipsi (P = 0.008). On multivariate analysis, V 5 ipsi was retained as the most significant factor. Concurrent chemoradiation caused significantly more RP than neoadjuvant chemoradiation (P = 0.004). A cutoff of 65% for V 5 ipsi had a sensitivity of 65% and a specificity of 91%. Conclusion: The correlation between pneumonitis and dosimetric constraints has been validated. Adding ipsilateral V 20 , V 5 , and MLD to the classical total lung constraints identifies patients likely to develop pulmonary toxicity in patients undergoing chemoradiation.