Stereotactic body radiation therapy (SBRT) for early-stage lung cancer

Stereotactic body radiation therapy (SBRT) is a new treatment modality for early-stage non-small-cell lung cancer, and has been developed in the United States, the European Union, and Japan. We started a feasibility study of this therapy in July 1998, using a stereotactic body frame. The eligibility criteria for primary lung cancer were: 1) solitary tumor less than 4 cm (T1-3N0M); 2) inoperable, or the patient refused operation; 3) no necessity for oxygen support; 4) performance status equal to or less than 2; 5) the peripheral tumor which dose constraints of mediastinal organs are maintained. A total dose of 48 Gy was delivered in four fractions in 2 weeks in most patients. Lung toxicity was minimal. No grade II toxicities for spinal cord, bronchus, pulmonary artery, or esophagus were observed. The 3 years overall survival for 32 patients with stage IA, and 13 patients with stage IB were 83% and 72%, respectively. Only one local recurrence was observed in a follow-up of 6-71 months. We retrospectively analyzed 241 patients from 13 Japanese institutions. The local recurrence rate was 20% when the biological equivalent dose (BED) was less than 100 Gy, and 6.5% when the BED was over 100 Gy. Overall survival at 3 years was 42% when the BED was less than 100 Gy, and 46% when it was over l00 Gy. In tumors, which received a BED of more than 100 Gy, overall survival at 3 years was 91% for operable patients, and 50% for inoperable patients. Long-term results, in terms of local control, regional recurrence, survival, and complications, are not yet evaluated. However, this treatment modality is highly expected to be a standard treatment for inoperable patients, and it may be an alternative to lobectomy for operative patients. A prospective trial, which is now ongoing, will, answer these questions.