Changes in lung function and perfusion after irradiation in patients with lung cancer.

The changes in lung function were prospectively studied for patients with lung carcinoma who were treated with relatively high doses of irradiation. Their dyspnoea score, lung volume spirometry, diffusion capacity and ipsilateral hemithorax perfusion were measured at presentation, again between 5 and 6 months after irradiation (Group 1, 36 evaluable patients), and once more between 11 and 12 months (Group 2, 16 evaluable patients). There was a worsening of the dyspnoea score from 1 to 2, in a large percentage of patients, but only 6% developed a dyspnoea score of 3. The largest change in lung function tests was a decrease in the diffusion capacity (DLCO) to 14% at 6 months and 12% at 12 months (statistically significant, P < 0.0001 paired t-test). The forced vital capacity (FVC) and the total lung capacity (TLC) showed a lesser decrease at 6 and 12 months, and the smallest decrease, which was not statistically significant, was in the forced expiratory volume in 1 s (FEV1). There was also a statistically significant decrease in the ipsilateral hemithorax lung perfusion of 16% at 6 months and 20% at 12 months. There was a weak correlation between the decrease in the DLCO and the FEV1 at follow-up. There was no statistically significant correlation between initial perfusion or decreased perfusion and the decrease in lung function. Lung irradiation should be regarded as an ablative form of therapy, analogous to surgery, in patients with a projected survival of 6 months or more. The DLCO is the most sensitive indicator of clinical damage and its pretreatment assessment should be useful in predicting clinical tolerance to irradiation.