The rapid advances in radiation oncology, radiation biology, and
radiation therapy physics have led to an accumulation of information on
the interactions of radiation with other therapeutic modalities, such as
the wide array of chemotherapeutic agents being employed in combination
with radiation therapy, as well as the multiple biologic response modi?
ers that are being used in combination with radiation therapy. It is now
recognized that they have a signi? cant impact on normal tissue
toxicities. The radiation doses customarily deemed safe on the basis of
past experience have now, when combined with other modalities, led to
severe late effects in different vital organs. The previously de? ned
radiation tolerance dosages remain as valuable guides, but their
applicability has changed signi? cantly. The emphasis is now placed on
the volume of the organ irradiated, as well as the dose being used. New
constructs rel- ing global (whole organ) and focal (partial volume)
injury as a function of the dose volume histogram emerge as a signi?
cant predictor of late effects on normal tissues. There are now
mathematical models such as the model on standard dose, time-dose
factors, and accumulated radiation effects that have been supplanted by
linear-q- dratic equations using the alpha/beta ratio and its clinical
applicability to normal tissue complications. This volume presents
contemporary data relating to late effects on normal tissues.