An applicator for delivering brachytherapy includes elongate members movable between collapsed and expanded configurations for delivering brachytherapy within a lumpectomy cavity, a vaginal cavity, or other target region. The elongate members may be expandable into a symmetrical or asymmetrical expanded configuration, e.g., into a generally spherical, pear-shaped, or planar configuration. A system for delivering brachytherapy includes the applicator and an access device for lining and/or dilating a body cavity and/or for receiving the applicator therein. The access device is advanced into a body cavity, an expandable member on the access device is inflated, the applicator is advanced into the access device, and the elongate members are expanded to deliver radiation to the target region. Alternatively, the access device carries an expandable device into the target region, the expandable device is removed after dilating the target region, and the applicator is introduced through the access device to deliver radiation.