Radiation pneumonitis following treatment of non-small-cell lung cancer with continuous hyperfractionated accelerated radiotherapy (CHART)

Purpose: To determine whether partial volume lung irradiation influences the risk of developing acute radiation pneumonitis after the treatment of non-small-cell lung cancer with continuous hyperfractionated accelerated radiotherapy (CHART). Methods and Materials: We conducted an analysis of 32 patients treated with CHART at the Gloucestershire Oncology Center. Twelve patients were treated using conventional two-dimensional treatment techniques and received elective nodal irradiation (ENI). Their treatment plans were subsequently recapitulated using a three-dimensional treatment planning system. Twenty patients were planned using this system from the outset. For these patients, elective nodal irradiation was omitted. Dose-volume histograms (DVH) were constructed and several parameters analyzed for their ability to predict for the development of pneumonitis. Results: Univariate analysis revealed that the percentage lung volume receiving more than 20 Gy (V 20 ) and the mean lung dose are of predictive value for the development of pneumonitis after CHART. There is a strong correlation between these two parameters. Importantly, partial volume lung irradiation using CHART appears to be better tolerated than conventionally fractionated radiotherapy. The omission of ENI considerably reduces V 20 . Using a commonly employed 3-beam technique it was also noted that the shape of the planning target volume (PTV) in the transverse plane (expressed as an elliptical index) affects the conformity of the V 20 isodose to the PTV. This influences the scope for dose escalation with irregularly shaped tumors. Conclusions: In relation to acute radiation pneumonitis, CHART appears to have a superior therapeutic index than conventionally fractionated radiotherapy. V 20 and mean lung dose are useful factors for predicting the risk of this complication. The use of these parameters will aid the selection of optimal treatment plans and provides a basis for future dose escalation studies.