Objective: To evaluate single photon emission computed tomography (SPECT) lung perfusion in predicting radiation pneumonitis in lung cancer patients.
Methods: From April 2003 to March 2004, 31 lung cancer patients treated with radical radiotherapy received SPECT lung perfusion scans, among whom, 23 had had perfusion scans both before and at the time of 40 Gy irradiation. The perfusion changes in the region of interest (ROI) after irradiation were obtained through comparing post-radiotherapy with pre-radiotherapy average proportion of SPECT counts within the ROI relative to average counts of the whole lung. Endpoint was defined as grade 2 and above radiation pneumonitis according to RTOG criteria.
Results: Lung perfusion defect was observed in all the patients at baseline. > or = grade 2 lung perfusion defect was found in 68.2% (15/22) of patients with central lesion and in 22.2% (2/9) of patients with peripheral lesions (P = 0.04). Seventy percent of the patients (16/23) experienced improved perfusion at 40 - 50 Gy. > or = grade 2 radiation pneumonitis was observed in 12 patients (38.7%) in the whole group, with 6 in those with grade 1 perfusion defects and another 6 in > or = grade 2 group, respectively; Of the 23 patients who had had both pre- and post-radiotherapy SPECT perfusion scan, 5 > or = grade 2 radiation pneumonitis occurred in the 16 perfusion-improved patients and 3 in the 7 unimproved patients.
Conclusion: There is no significant correlation between radiation pneumonitis and the extent of perfusion defect either before or after 40 - 50 Gy irradiation based on our limited data analysis in this series.