Combinations of external beam radiotherapy and interstitial or intracavitary brachytherapy have been effectively used in variety of clinically settings since the introduction of megavoltage beam therapy in the 1950s. Generally, brachytherapy is used to administer high doses to unresected or residual primary tumor while external beamradiotherapy is used to delivermore modest doses to larger volumes of adjacent tissue or regional lymph nodes at high risk for microscopic invasion. Conventionally, relatively simple external beam field arrangements are used to administer uniformdoses to the region treated by brachytherapy. The dose conformality and normal tissue avoidance needed to make the high total tumor dose tolerable is generally provided by the brachytherapy component of treatment. Usually, the brachytherapy and external beam components of treatment are planned independently of one another.