Intraindividual comparison of conventional three-dimensional radiotherapy and intensity modulated radiotherapy in the therapy of locally advanced non-small cell lung cancer - A planning study

Background: Local failure is the one of the most frequent cause of tumor related death in Locally advanced non-small cell Lung cancer (LAD-NSCLC). Dose escalation has the promise of increased loco-regional tumor control but is Limited by the tolerances of critical organs. Patients and Methods: To evaluate the potential of IMRT in comparison to conventional three-dimensional conformal planning (3DCRT) dose constraints were defined: Maximum dose (D-max) to spinal cord < 48 Gy, mean Lung dose less than or equal to 24 Gy, D-max esophagus >70 Gy in not more than 5 cm of the total length. For ten patients two plans were compared: (1) 3DCRT with 5 weekly fractions (SD) of 2 Gy to a total dose (TD) of 50 Gy to the planning target volume of second order (PTV2). If the tolerance of the critical organs was not exceeded, patients get a boost plan with a higher TD to the PTV1. (2) IMRT: concomitant boost with 5 weekly SD of 2 Gy (PTV1) and 1.5 Gy to a partial (p)PTV (pPTV = PTV2 boolean AND PTV1) to a TD of 51 Gy to the pPTV and 68 Gy to the PTV1. If possible, patients get a boost plan to the PTV1 with 5 weekly SD of 2 Gy to the highest possibly TD. Results: Using 3DCRT, 3/10 patients could not be treated with TD > 50 Gy, but 9/10 patients get higher TD by IMRT. TD to the PTV1 could be escalated by 16% on average. The use of non-coplanar fields in IMRT Lead to a reduction of the irradiated Lung volume. There is a strong correlation between physical and biological mean lung doses. Conclusion: IMRT gives the possibility of further dose escalation without an increasing mean Lung dose especially in patients with large tumors.