An evaluation of two techniques for beam intensity modulation in patients irradiated for stage III non-small cell lung cancer

In locally advanced lung cancer, the use of high dose radiotherapy (RT) and/or concurrent chemo-RT is associated with significant pulmonary and esophageal toxicity. Despite a 3D conformal RT technique and the omission of elective mediastinal fields, three (of ten) patients with inoperable stage 3 NSCLC who were treated with induction chemotherapy (carboplatin-paclitaxel) followed by RT to 70 Gy, developed symptomatic radiation pneumonitis. In this planning study, the actual treatment plans of all ten patients were compared to plans derived using two beam intensity-modulated (BIM) techniques, for which similar geometrical beam setup parameters were used. In the first technique (BF-BIM), cranial and caudal boost fields were applied in order to allow field length reduction. The second technique (C-BIM) utilised 3-D missing-tissue compensators for all radiation beams. Both BIM techniques resulted in a significant sparing of critical normal tissues and the C-BIM technique was superior in all cases. When compared to the actual RT technique used for treatment, a reduction of 8.1±4.7% (1 S.D.) was observed in the mean lung dose for the BF-BIM plan, vs. 20.3±5.8% (1 S.D.) for the C-BIM plan. Similar reductions were observed in the percentage of the total lung volume exceeding 20 Gy (V₂₀) for these techniques. BIM techniques appear to be a promising tool for enabling radiation dose-escalation and/or intensive concurrent chemo-RT in inoperable lung cancer.