[Optimal thoracic irradiation for stage IV lung cancer]

To investigate optimal thoracic irradiation (TI) for stage IV lung cancer, we retrospectively reviewed 150 patients. In all, 101 patients underwent radiotherapy for the primary lesion, and 130 had radiotherapy for metastasized sites. TI fields were basically divided into two groups; whole thoracic lesion irradiation (WTLI) and partial thoracic lesion irradiation (PTLI). Overall survival rates at 6 months, 1 year and 2 years were 58%, 27% and 11%, respectively, and MST was 7.1 months. There was no difference in survival according to histological type. On univariate analysis, the factors of good prognosis included good PS, free of bone metastasis, metastasis limited to a single organ, TI, chemotherapy, age (less than or equal to 75 years), and TN factors (T0-2 and N0-1). Multivariate analysis showed PS was the predominant factor. Among the patients treated with TI, survival rates of patients with PS 0-1 were superior to those of patients with PS 2-4. Radiation pneumonitis was more frequent in WTLI than in PTLI. The rates of thoracic failure death were 31.7% in patients treated with TI and 63.3% without TI. However, the size of the thoracic radiation field did not affect the rates of thoracic failure death. We concluded that TI for stage IV patients could reduce thoracic symptoms and increase the survival rate in the subgroup with good PS. Furthermore, we considered PTLI was worth while in the subgroup with poor PS.