Superiority of conventional intensity-modulated radiotherapy over helical tomotherapy in locally advanced non-small cell lung cancer A comparative plan analysis

Purpose. To compare helical tomotherapy (HT) and conventional intensity-modulated radiotherapy (IMRT) using a variety of dosimetric and radiobiologic indexes in patients with locally advanced non-small cell lung cancer (LA-NSCLC).Patients and methods. A total of 20 patients with LA-NSCLC were enrolled. IMRT plans with 4-6 coplanar beams and HT plans were generated for each patient. Dose distributions and dosimetric indexes for the tumors and critical structures were computed for both plans and compared.Results. Both modalities created highly conformal plans. They did not differ in the volumes of lung exposed to >20 Gy of radiation. The average mean lung dose, volume receiving ≥30 Gy, and volume receiving ≥10 Gy in HT planning were 18.3 Gy, 18.5%, and 57.1%, respectively, compared to 19.4 Gy, 25.4%, and 48.9%, respectively, with IMRT (p=0.004, p<0.001, and p<0.001). The differences between HT and IMRT in lung volume receiving ≥10-20 Gy increased significantly as the planning target volume (PTV) increased. For 6 patients who had PTV greater than 700 cm³, IMRT was superior to HT for 5 patients in terms of lung volume receiving ≥5-20 Gy. The integral dose to the entire thorax in HT plans was significantly higher than in IMRT plans.Conclusion. HT gave significantly better control of mean lung dose and volume receiving ≥30-40 Gy, whereas IMRT provided better control of the lung volume receiving ≥5-15 Gy and the integral dose to entire thorax. In most patients with PTV greater than 700 cm3, IMRT was superior to HT in terms of lung volume receiving ≥5-20 Gy. It is therefore advised that caution should be exercised when planning LA-NSCLC using HT.