Interim analysis and monitoring
Two interim analyses considering multiplicity will be conducted using the Lan and DeMets method along with the O’Brien and Fleming-type alpha spending function [In the first interim analysis, if both the non-inferiority and superiority of the experimental arm over the standard arm in terms of the primary endpoint are demonstrated with an adjusted alpha level, the study will be terminated. If the non-inferiority of the experimental arm at the primary endpoint is not demonstrated or its non-inferiority but not superiority is demonstrated, the study will be continued. In the second interim analysis, the study will be terminated if the non-inferiority of the experimental arm to the standard arm in the primary endpoint is demonstrated with an adjusted alpha level. If the non-inferiority of the experimental arm in the primary endpoint is not demonstrated, the study will be continued. In both interim analyses, if the point estimate of the hazard ratio of TTF1 exceeds the non-inferiority margin (1.32), the study will be terminated because of futility.In-house monitoring will be performed every 6 months by the JCOG Data Center to evaluate and improve study progress, data integrity, and patient safety. All enrolled patients are evaluated for compliance with the RT protocol at the time of completion of RT. The purpose of this assessment is to confirm whether the actual treatment at each participating institution is performed according to the protocol regulations and to provide feedback for the treatment of subsequently enrolled patients.