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Modern advances in computers have fueled parallel advances in imaging technologies. The improvements in imaging have in turn allowed a higher level of complexity to be incorporated into radiotherapy treatment planning systems. As a result of these changes, the delivery of radiotherapy evolved from therapy designed based primarily on plain (two dimensional) x-ray images and hand calculations to three-dimensional x-ray based images incorporating increasingly complex computer algorithms. More recently, biologic variables based on differences between tumor metabolism, tumor antigens, and normal tissues have been incorporated into the treatment process. In addition, greater awareness of the challenges to the accuracy of the treatment planning process, such as problems with set-error and organ movement, have begun to be systematically addressed, ushering in an era of so-called FourDimensional Radiotherapy. This review article discusses how these advances have changed the way the most common neoplasms are treated now and will be treated in the near future. (CA Cancer J Clin 2005;55:117-134.)

Purpose To evaluate the efficacy and adverse effects of image-guided stereotactic body radiation therapy (SBRT) in centrally/superiorly located non–small-cell lung cancer (NSCLC). Methods and Materials We delivered SBRT to 27 patients, 13 with stage I and 14 with isolated recurrent NSCLC. A central/superior location was defined as being within 2 cm of the bronchial tree, major vessels, esophagus, heart, trachea, pericardium, brachial plexus or vertebral body but 1 cm away from the spinal canal. All patients underwent four-dimensional CT–based planning, and daily CT-on-rail guided SBRT. The prescribed dose of 40 Gy (n=7) to the planning target volume was escalated to 50 Gy (n=20) in 4 consecutive days. Results With a median follow-up of 17 months (range, 6–40 months), the crude local control at the treated site was 100% using 50 Gy. However, three of seven patients had local recurrences when treated using 40 Gy. Of the patients with stage I disease, one (7.7%) and two (15.4%) developed mediastinal lymph node metastasis and distant metastases, respectively. Of the patients with recurrent disease, three (21.4%) and five (35.7%) developed mediastinal lymph node metastasis and distant metastasis, respectively. Four patients (28.6%) with recurrent disease but none with stage I disease developed grade 2 pneumonitis. Three patients (11.1%) developed grade 2–3 dermatitis and chest wall pain. One patient developed brachial plexus neuropathy. No esophagitis was noted in any patient. Conclusion Image-guided SBRT using 50 Gy delivered in four fractions is feasible and resulted in excellent local control.