Phase I study of stereotactic body radiation therapy for centrally located stage IA non-small cell lung cancer (JROSG10-1)

To investigate the maximum tolerated dose (MTD) and recommended dose (RD) of stereotactic body radiation therapy (SBRT) for centrally located stage IA non-small cell lung cancer (NSCLC). Five dose levels, ranging from of 52 to 68 Gy in eight fractions, were determined; the treatment protocol began at 60 Gy (level 3). Each dose level included 10 patients. Levels 1-2 were indicated if more than four patients exhibited dose-limiting toxicity (DLT), which was defined as an occurrence of a grade 3 (or worse) adverse effect within 12 months after SBRT initiation. MTD was defined as the lowest dose level at which more than four patients exhibited DLT. Ten patients were enrolled in the level 3 study. One patient was considered unsuitable because of severe emphysema. Therefore, nine patients were evaluated and no patient exhibited DLT. The level 3 results indicated that we should proceed to level 4 (64 Gy). However, due to the difficulty involved in meeting the dose constraints, further dose escalation was not feasible and the MTD was found to be 60 Gy. The RD of SBRT for centrally located stage IA NSCLC was 60 Gy in eight fractions.