Basic and technical research on lung cancer

In association with clinical study of carbon beam therapy for lung cancer, the basic research for lung cancer and the patients with this disease has been carried out for the past 10 years. With regard to lung damage by the carbon beams, firstly pulmonary function was measured and analyzed for the patients with stage I non-small cell lung cancer. Force expiratory volume in 1 second (FVE 1.0) and TLC (total lung capacity) was found to be reduced significantly at 6 and 12 months after therapy but the reduction rate was a little, which can support the safety of this treatment modality. Secondly, the regional lung damage by the beams was investigated by using correct fusion of CT images with carbon beam dose distribution, diagnostic follow-up CT images and blood flow and ventilation spect images. It demonstrated the graded decrease blood flow by dose and the compensatory increase of blood flow in the adjacent lobe of lung unexposed to irradiation. On the other hand, the biological study of carbon beam effects on lung cancer cells and tumors line was conducted. Firstly, by using 7 or 4 human lung cancer cell line, the radiosensitivity of carbon beams was compared with that of photons by different histological patterns. It was found that there was no essential difference in the sensitivity pattern for lung cancer histology between the carbon beams and photons though the former doubled the later in power. Secondly, by using IA cell lines among them, the dynamic of clonogenic cells (clonogen) in a nude tumor and the changes in its morphology following irradiation was investigated, clarifying that the clonogen proliferating under anoxic or hypoxic conditions played a pivotal role for tumor regrowth and stemmed from the different clone which had been genetically selected and developed under these conditions. The finding of clonogen becomes one of the evidence supporting the superiority of a single-dose radiotherapy to fractionated radiotherapy. (author)