Purpose: To determine local dose-effect relations for lung perfusion and density changes due to irradiation for patients with non-small-cell lung cancer (NSCLC) and to quantify the effect of reperfusion.
Methods and materials: For 25 NSCLC patients and a reference group of 81 patients with healthy lungs, registered single photon emission computed tomography (SPECT) lung perfusion and CT scans were made, before and after radiotherapy. Average dose-effect relations for perfusion and CT-density changes were calculated and compared with the dose-effect relation of the reference group. On the basis of these dose-effect relations, the post-RT perfusion was predicted for each patient and compared to the measured post-RT perfusion.
Results: Well-perfused lung regions of the NSCLC patients showed the same dose-effect relation as the reference patients. By comparing predicted and measured post-treatment perfusion scans, regions of reperfusion could be determined for 18 of 25 NSCLC patients but for none of the reference patients.
Conclusion: Well-perfused lung tissue of patients with NSCLC behaves like healthy lung tissue with respect to radiation. The dose-effect relation for perfusion and CT density was extended for doses up to 80 Gy. Radiation damage in poorly perfused lung regions was less than predicted as a consequence of local reperfusion.