Dose escalation of chart in non-small cell lung cancer: is three-dimensional conformal radiation therapy really necessary?

PURPOSE: To evaluate, preclinically, the potential for dose escalation of continuous, hyperfractionated, accelerated radiation therapy (CHART) for non small-cell lung cancer (NSCLC), we examined the strategy of omission of elective nodal irradiation with and without the application of three-dimensional conformal radiation technology (3DCRT). METHODS AND MATERIALS: 2D, conventional therapy plans were designed according to the specifications of CHART for 18 patients with NSCLC (Stages Ib, IIb, IIIa, and IIIb). Further plans were generated with the omission of elective nodal irradiation (ENI) from the treatment portals (2D minus ENI plans [2D-ENI plans]). Both sets were inserted in the patient's planning computed tomographies (CTs). These reconstructed plans were then compared to alternative, three-dimensional treatment plans which had been generated de novo, with the omission of ENI: 3D minus elective nodal irradiation (3D-ENI plans). Dose delivery to the planning target volumes (PTVs) and to the organs at risk were compared between the 3 sets of corresponding plans. The potential for dose escalation of each patient's 2D-ENI and 3D-ENI plan beyond 54 Gy, standard to CHART, was also determined. RESULTS: PTV coverage was suboptimal in the 2D CHART and the 2D-ENI plans. Only in the 3D-ENI plans did 100% of the PTV get > or = 95% of the dose prescribed (i.e., 51.5 Gy [51.3-52.2]). Using 3D-ENI plans significantly reduced the dose received by the spinal cord, the mean and median doses to the esophagus and the heart. It did not significantly reduce the lung dose when compared to 2D-ENI plans. Escalation of the dose (minimum > or = 1 Gy) with optimal PTV coverage was possible in 55.5% of patients using 3D-ENI, but was possible only in 16.6% when using the 2D-ENI planning strategy. CONCLUSIONS: 3DCRT is fundamental to achieving optimal PTV coverage in NSCLC. A policy of omission of elective nodal irradiation alone (and using 2D technology) will not achieve optimal PTV coverage or dose escalation. 3DCRT with omission of ENI can achieve true escalation of CHART in 55.5% of tumors, depending on their site and N-stage.

The impact of three-dimensional radiation on the treatment of non-small cell lung cancer.

PURPOSE: Non-small cell lung cancer (NSCLC) patients with locally advanced unresectable disease have a grim prognosis. Radiotherapeutic strategies are necessary to improve the permanent eradication of thoracic disease. The poor results achieved with conventional external beam radiation therapy reflect in part, the inadequacy of such therapy in achieving its primary objective of achieving local control. The impact of three-dimensional conformal radiation therapy (3-DCRT) on local disease eradication and its potential role in improving survival is assessed. DESIGN: This review addresses aspects of the software and hardware technology of 3-DCRT, the clinical and technical aspects of target volume definition, the use of 3-DCRT to predict radiation pneumonitis, strategies for dose escalation in NSCLC, and analyses the clinical results to date. RESULTS: Initially investigators compared the best treatment techniques devised with conventional planning techniques to those devised with 3-DCRT. These analyses showed that 3-DCRT had the potential to deliver high dose radiation (>70 Gy) with minimal underdosing and with a concomitant relative sparing of normal tissues. This technical demonstration of enhanced therapeutic ratio is the basis for the evolving clinical utilization of 3-DCRT for NSCLC. Software and hardware developments continue to develop and have the potential to solve evolving clinical issues. Dose-volume-histograms have been used to accurately quantify lung dose and derived parameters have the potential to predict the risk of pneumonitis for individual patients before treatment. Initial clinical results have been promising and strategies for further dose escalation are emerging. CONCLUSION: Preliminary experience has resulted in promising survival following three-dimensional conformal radiation therapy alone for locally advanced NSCLC. More follow-up and experience will determine late toxicity, maximum dose, and efficacy of dose escalation with three-dimensional conformal radiation therapy. Strategies should be developed to integrate this modality into the combined treatment of locally advanced non-small cell lung cancer.