Stereotactic body radiation therapy for lung cancer: achievements and perspectives.

Stereotactic body radiation therapy is a new treatment modality where narrow beams from several directions focus on the target while sparing the adjacent normal tissues with high accuracy. This technique basically derived from that of radiosurgery for intracranial lesions allows us to deliver high dose to the target leading to high control of the tumor without causing significant cytotoxicities associated with the treatment. Early-stage non-small cell lung cancers are regarded as most appropriate malignancies for this modality and accordingly have most intensively been investigated. With many encouraging outcomes in retrospective studies, several prospective clinical trials have been started world-wide. Japan Clinical Oncology Group protocol 0403 is a phase II trial of stereotactic body radiation therapy for T1N0M0 non-small cell lung cancer including both inoperable and operable patients. The results for operable patients are to be disclosed this year after 3 years of follow-up. It is highly probable that stereotactic body radiation therapy can be a standard treatment modality for inoperable patients for early-stage non-small cell lung cancer. The role of stereotactic body radiation therapy for operable patients is expected to be clarified by the outcomes of coming clinical trials. Tremendous advance in stereotactic body radiation therapy is expected when four-dimensional radiation therapy coping with tumor movement is realized. Among several approaches, tumor tracking appears most ideal. The new image-guided radiotherapy system which has the capability of tumor tracking has been developed in Japan.