THE ADVANTAGES OF 3-DIMENSIONAL CONFORMAL RADIOTHERAPY FOR TREATMENT OF CHILDHOOD-CANCER

Three-dimensional treatment planning with delivery of conformal radiot herapy has been demonstrated to improve tumor targeting and to reduce normal tissue volume exposed in several studies of malignancies in adu lts. Furthermore, institutional clinical protocols have accomplished e scalation of radiation dose with enhanced treatment efficacy and stabl e to decreased late effects in patients with prostate carcinoma. In th e treatment of malignancies in children, there are several aspects of therapy which may be particularly amenable to improvement with three-d imensional treatment planning. First, the occurrence of large, irregul ar tumor volumes close to critical normal structures is common in soli d tumors in children. The acquisition of detailed computerized tomogra phy (CT) images at the time of simulation, along with the use of three -dimensional reconstruction and beam's-eye-view capabilities, should g reatly improve tumor targeting and allow more selective blocking of no rmal structures. In addition, the enhanced sensitivity of developing o rgans and tissues to radiation in combination with high expectations f or overall survival with current treatment programs has resulted in gr eater awareness of the late effects of treatment. Today, the goal of p ediatric radiotherapy is to provide high rates of local tumor control without significant late effects, such as impairment of growth and dev elopment and injury to organ function. The use of conformal radiothera py is likely to be an important advance in realizing this goal. The ab ility to use novel beam arrangements and to evaluate radiotherapy trea tment plans with quantitative tools, such as dose-volume histogram ana lysis or probabilities of normal tissue complications, should enable t he use of treatment programs with a lessened risk of late effects. How ever, the rarity of pediatric tumors is unlikely to permit a controlle d trial of conformal compared to conventional therapy. In this article , we use three case illustrations to demonstrate and discuss the poten tial advantages of conformal radiotherapy in the treatment of childhoo d cancer. (C) 1998 by Radiation Research Society.