Advances in radiation therapy

Abstract

Before discussing recent advances in radiation therapy, it is important to consider the basic principles. The design for a proper course of radiation therapy must consider the extent of extrathyroidal disease and the location of lymph node disease, as well as the radiation tolerance of normal tissues and organs. The accepted terminology to describe the radiation dose and target volume in the planning of radiotherapy is summarized in Table 1. The principle is to deliver the prescribed dose to the entire clinical target volume (CTV) with a reasonable dose uniformity (±5%). Customdesigned fields should be used to conform to the target volume while keeping the volume of irradiated normal tissues to a minimum. In general, the aim should be to deliver 5000-6000 rad (50-60 Gy) to the CTV and 6000-7000 rad (60-70 Gy) to the gross tumor volume (GTV) in 1800-2000 rad (1.8-2.0 Gy) fractions over 5-7 wk (1-6). External radiation therapy is delivered with linear accelerators generating X-ray beams in the megavoltage range of 4-25 MV (photons). © 2006 Humana Press Inc.