A base station apparatus (1) is configured to send a first information element to an inter-base-station gateway (3). The first information element explicitly or implicitly indicates whether a relay operation is necessary. The relay operation is an operation in which the inter-base-station gateway (3) relays a data packet destined for or sent from a radio terminal between the base station apparatus (1) and another base station (2). It is thus, for example, possible to contribute to enabling a base station or an inter-base-station gateway to select whether a relay operation by the inter-base-station gateway should be performed at the time of an inter-base-station handover.