Devices and methods are provided for applying vacuum near to devices for delivering treatments to tissue adjacent a body cavity, effective to draw adjacent tissue near to such devices and to enhance treatment of the tissue. Body cavities include natural body cavities and cavities remaining after removal of tissue such as cancerous tissue. A device may include an inner balloon assembly with an inflation conduit. A sheath assembly having a fluid-permeable sheath wall may enclose the inner balloon assembly. Vacuum applied to the space between the sheath and the inner balloon is useful to draw tissue into contact with the device, improving treatment effectiveness. Methods for treating tissue with such devices and systems are also provided. Treatments may include providing radioactive material for radiation treatment, providing chemotherapeutic material for chemotherapy, providing thermal treatment, and combinations thereof. Systems may include devices of the invention and a vacuum source.