RT Book, Section A1 Hill, Richard P. A1 Bristow, Robert G. A2 Tannock, Ian F. A2 Hill, Richard P. A2 Bristow, Robert G. A2 Harrington, Lea SR Print(0) ID 1127473049 T1 Tumor and Normal Tissue Response to Radiotherapy T2 The Basic Science of Oncology, 5e YR 2016 FD 2016 PB McGraw-Hill Education Medical PP New York, NY SN 9780071745208 LK accessbiomedicalscience.mhmedical.com/content.aspx?aid=1127473049 RD 2024/03/28 AB The dose of radiation that can be delivered to a tumor is limited by the damage caused to surrounding normal tissues and the consequent risk of complications. Whether a certain risk of developing complications is regarded as acceptable depends both on the function of the tissue(s) and the severity of the damage involved. This risk must be compared to the probability of benefit (ie, eradicating the tumor) to determine the overall gain from the treatment. This gain can be estimated for an average group of patients, but it may vary for individual patients, depending on the particular characteristics of their tumors and the normal tissues at risk. The balance between the probabilities for tumor control and normal tissue complications gives a measure of the therapeutic ratio of a treatment (see Sec. 16.5.8). The therapeutic ratio can be improved either by increasing the effective radiation dose delivered to the tumor relative to that given to surrounding normal tissues, or by increasing the biological response of the tumor relative to that of the surrounding normal tissues (see Figs. 16–1, 16–2, 16–3).