A brachytherapy device is provided for treating a target tissue through an external surface area of the target tissue. The device includes an insertion member having a proximal portion, a distal portion, and at least one lumen extending therethrough. A fluid retaining member is mated to the distal portion of the insertion member and has a first surface shaped to conform to a predetermined external surface area of a tissue to be treated, and a cavity formed therein in fluid communication with the at least one lumen in the insertion member. A plurality of anchor members can be distributed about a periphery of the first surface to anchor the first surface to an external surface area of a tissue to be treated.