Clinical Applications of Molecular Biology in Radiation Oncology

As oncologists, our ability to understand and treat cancer will change dramatically over the next few decades. The fields of molecular, cellular, and cancer biology are rapidly changing, bringing forth new concepts regarding the basic mechanisms of oncogenesis, and with them, totally novel opportunities for therapeutic intervention. A general knowledge of the terms and concepts of the new biology is essential to radiation oncologists because these are already in our daily practice in the form of questions from our patients regarding the newest findings, assays of prognostic and predictive factors, and potential new therapies to deliver or augment radiation therapy. The classic radiation biology observations remain true-cell cycle perturbation, hypoxia, variation in cell survival after radiation, the competition model, fractionation effects, normal tissue injury, and so forth. The techniques available from the new biology enable us to elucidate the basic mechanisms underlying these observations. The current classes of radiation modifiers-halopyrimidines, hypoxic modifiers, radioprotectors, and combined modality therapy-will be supplemented by modifiers of signal transduction, cell cycle arrest, apoptosis, angiongenesis, and the stress response, to name a few.