Brachytherapy treatment of a patient's lung tissue following resection is effected using a balloon applicator which is inserted, normally through the same opening used for the surgery, through the chest wall and into the cavity. The lung and chest openings are closed around the applicator and generally sealed around the applicator. A suction port is provided, in a suction circuit of the applicator, to withdraw fluid from the pleural cavity, at intervals as needed, to assure that the lung can be inflated. Different embodiments of suction circuits are disclosed. A bronchial applicator and method are also disclosed.