Uncertainties in radiation therapy: target volume definition in prostate cancer

Accurate definition of target volumes and pelvic organs at risk is critical to improve the outcome in patients treated with irradiation for localized carcinoma of the prostate. Precise delineation of these structures will assist in more rational therapeutic decisions and optimized radiation therapy treatment planning and delivery. Increased conformity in radiation dose distribution allows delivery of higher doses of irradiation and dose escalation studies and results in improved tumor control, lower incidence of distant metastasis, improved survival and better quality of life. Multiple imaging methods are available and significant advances have been made in image fusion to enhance target volume definition. An exhaustive review of the literature is presented.