A compound for use in the treatment of tumors, where the compound is represented by the general formula (1) indicated below or a salt thereof: [Formula 1] where X1 represents a nitrogen atom or a -CH group >； =, R1 represents a group -Z-R6, Z represents a group -N (R8) -B-, R8 represents a hydrogen atom, a C1-C6 alkyl group that can have a C1-C6 alkoxy group as a substituent , a C1-C6 alkanoyl group, a C1-C6 alkylsulfonyl group or a C1-C6 alkyl phenyl group, B represents a -CO- group or a C1-C6 alkylene group, R6 represents a saturated monocyclic, dicyclic or tricyclic heterocyclic group or unsaturated 5 to 15 members having 1 to 4 nitrogen atoms, oxygen atoms or sulfur atoms (which may have 1 to 3 substituents, which are selected from the group consisting of an oxo group； a C1 alkoxy group -C6 which can have a halogen atom as a substituent； a C1-C6 alkyl group that can have a halogen atom as a substituent； a halogen atom； a C1-C6 alkylsulfonyl group； a phenyl group that may be substituted by a C1-C6 alkyl group that may have a halogen atom in the phenyl ring； a C1-C6 alkylthio group, a pyrrolyl group, a benzoyl group； a C1-C6 alkanoyl group； a C1-C6 alkoxycarbonyl group； and an amino group which may have a group selected from the group consisting of a C1-C6 alkyl group and a C1-C6 alkanoyl group as a substituent, in the heterocyclic ring), an adamantyl group, a naphthyl group (which may have from 1 to 3 groups selected from the group consisting of a C1-C6 alkyl group, a halogen atom, and an amino group which may have a group selected from the group consisting of a C1-C6 alkyl group and an alkanoyl group C1-C6 as a substituent, in the naphthalene ring), an alkyl group that may have a C1-C6 alkoxy group as a substituent, a cycloalkyl group that may be substituted by a group selected from the group consisting of an amino alkyl group -substituted C1-C6 which can have a C1-C6 alkyl group and a C1-C6 alkyl group which can have a halogen atom as a substituent, in the cy
