A prospective study of whether radiation pneumonitis is influenced by low-dose irradiated lung volume in primary lung cancer with chronic pulmonary disease.

The current study prospectively investigated the optimal dose-volume condition in cases of lung cancer with chronic pulmonary disease compared to those without chronic pulmonary disease. Cases of primary lung cancer treated with intended curative radiation therapy were registered in the current study. Their fraction size was limited to 2-3 Gy, so-called standard fractionation. They were prescribed a total dose of 60 Gy for non-small cell lung cancer (NSCLC; n=17) and a total dose of 54 Gy for small cell lung cancer (SCLC; n=4). Of the 21 patients enrolled in this study, 4 had chronic pulmonary disease (study arm), and the others had no chronic pulmonary disease (control arm). Seven received chemotherapy. Symptomatic radiation pneumonitis occurred in 5. Of the four patients in the study arm, two (50%) experienced symptomatic radiation pneumonitis; only 3 of the 17 patients in the control arm (17.6%) experienced symptomatic radiation pneumonitis. Furthermore, the median V(20) of patients who experienced symptomatic radiation pneumonitis in the study arm was 14%, which was higher than that of patients with no symptomatic radiation pneumonitis in the study arm, 5.8%. On the other hand, in the control arm, the median V(20) of patients with symptomatic radiation pneumonitis was 14.2%, about the same as that of patients with no symptomatic radiation pneumonitis in the control arm, 15.1%. The current study suggested that, as much as 15% of V(20), might play an important role in cases of lung cancer with chronic pulmonary disease.