Today we will master primary vaginal cancer from first principles to planning. We will start with epidemiology, pathophysiology, and the anatomy that dictates nodal targets. We will explain why definitive radiation is the backbone of curative therapy for most stages. Then we will design a complete plan that combines pelvic EBRT with a brachytherapy boost, including when to choose an interstitial implant rather than a cylinder. By the end, you will be able to choose the correct nodal basins based on tumor location, justify definitive radiation over morbid surgery, and construct a curative EBRT and brachy plan to seventy to eighty-five gray with the right applicator for the residual tumor thickness.