Can 99mTc-DTPA aerosol scanning predict radiation pneumonitis?

To investigate whether changes in diethylenetriamine pentaacetic acid (DTPA) aerosol clearance lung scans predict the development of radiation pneumonitis.

Thirty-three patients with advanced non-small-cell lung cancer were treated with palliative radiation therapy to thorax. All patients were subjected to pretreatment and post-treatment DTPA aerosol clearance lung scans. The clearance t1/2 values were compared using the paired t test. Changes in percentage aerosol deposition were also compared. The patients were serially assessed clinically and radiologically for development of radiation pneumonitis.

For the whole group, the mean DTPA clearance t1/2 for the diseased lung fell from 36.33 to 28.85 min (p = 0.17). Twelve patients developed radiation pneumonitis, 8 Grade 1, 2 Grade 2, 1 Grade 3, and 1 Grade 4. In patients who developed radiation pneumonitis, the clearance t1/2 for the diseased lung decreased from 37.50 min to 29.00 min after treatment (p = 0.50). Other subgroups analyzed, including smokers, nonsmokers, those with and without endobronchial disease, as well as those free from radiation pneumonitis, also showed no significant change in the clearance of the aerosol. The difference between the percentage aerosol deposition of the diseased lung (37.92%) and that of the opposite lung (62.08%) for the entire sample was significantly different both before and after treatment (p < 0.01). Delivery of radiation did not significantly change the aerosol deposition in either lung.

We conclude that, in patients with advanced non-small-cell lung cancer, significant change in the pulmonary clearance of 99mTc-DTPA aerosol could not be demonstrated after radiation therapy. In such patients, clearance of the aerosol does not predict the development of radiation pneumonitis.