This is Episode 17: Therapeutic Ratio & Predictive Assays. In our previous episodes, we've explored how radiation interacts with cells and tissues, the different types of damage it causes, and how cells attempt to repair that damage. We've also seen that different tissues, both normal and malignant, respond differently to radiation. The ultimate goal in radiation therapy is to deliver a dose that is high enough to eradicate all cancer cells while minimizing damage to surrounding healthy normal tissues. This delicate balance is what we call the therapeutic ratio. Today, we're going to define this crucial concept, look at how it's visualized using Tumor Control Probability and Normal Tissue Complication Probability curves, explore the factors that influence these probabilities, and discuss assays that aim to predict these responses, thereby helping us personalize and optimize treatment for our patients. We'll also touch upon how radioprotectors and radiosensitizers aim to improve this therapeutic ratio.