A brachytherapy device for the provision of brachytherapy is disclosed. The brachytherapy device has at least one source lumen located outside a movable surface of the device. The source lumen may be secured to the movable outer surface in a manner whereby relative movement of the source lumen relative to the movable outer surface is permitted. The brachytherapy device is inserted into a body cavity. After insertion, the movable surface is moved to position the at least one source lumen closer to the tissue boundary of the cavity. One or more sources of radiation are then placed within the at least one source lumen to provide a customizable treatment. Also disclosed are methods for providing brachytherapy via body cavities.