Effects of radiotherapy planning with a dedicated combined PET-CT-simulator of patients with non-small cell lung cancer on dose limiting normal tissues and radiation dose-escalation: a planning study.

Abstract

To investigate the effect of radiotherapy planning with a dedicated combined PET-CT simulator of patients with locally advanced non-small cell lung cancer. Twenty-one patients underwent a pre-treatment simulation on a dedicated hybrid PET-CT-simulator. For each patient, two 3D conformal treatment plans were made: one with a CT based PTV and one with a PET-CT based PTV, both to deliver 60Gy in 30 fractions. The maximum tolerable prescribed radiation dose for CT versus PET-CT PTV was calculated based on constraints for the lung, the oesophagus, and the spinal cord, and the Tumour Control Probability (TCP) was estimated. For the same toxicity levels of the lung, oesophagus and spinal cord, the dose could be increased from 55.2+/-2.0Gy with CT planning to 68.9+/-3.3Gy with the use of PET-CT (P=0.002), with corresponding TCP's of 6.3+/-1.5% for CT and 24.0+/-5.6% for PET-CT planning (P=0.01). The use of a combined dedicated PET-CT-simulator reduced radiation exposure of the oesophagus and the lung, and thus allowed significant radiation dose escalation whilst respecting all relevant normal tissue constraints.