Inclusion of functional information from perfusion SPECT improves predictive value of dose-volume parameters in lung toxicity outcome after radiotherapy for non-small cell lung cancer: A prospective study.

BACKGROUND AND PURPOSE: To compare functional and standard dose-volume parameters as predictors of postradiation pulmonary toxicity in lung cancer patients undergoing curative chemo-radiotherapy (RT) studied prospectively.

MATERIAL AND METHODS: A total of 58 patients treated with Intensity Modulated RT (60-66Gy) were analysed. Standard dose-volume parameters were extracted from treatment planning computed tomography (CT) scans. Corresponding functional dose-volume parameters were calculated from perfusion single-photon emission computed tomography (SPECT). Primary end-point was radiation pneumonitis (RP) grade 2-5.

RESULTS: Functional mean lung dose (MLD) and lung volumes receiving 5, 10, 20 and 30Gy (V5-V30, respectively) revealed high correlation with corresponding standard parameters (r>0.8). Standard MLD, V20 and V30 were significantly higher in patients with RP (p=0.01). All functional parameters were significantly higher in the RP patients (p<0.03). In multivariate analysis functional parameters produced superior risk estimates, while all standard parameters, except V30, were not related to the risk of RP. Area under the curve (AUC) for functional metrics generally exceeded the AUC for corresponding standard parameters, but they were not significantly different from each other.

CONCLUSION: SPECT-based functional parameters were better to predict the risk of RP compared to standard CT-based dose-volume parameters. Functional parameters may be useful to guide radiotherapy planning in order to reduce the risk of radiation-induced toxicity.