Guidelines for Complications of Cancer Treatment Vol VIII Part B

acceptability of the types of treatment related morbidity.Having in mind this fact, to say a dose to the spinal cord of 45Gy in 23-25 fraction represents cord tolerance, is true onlyinsofar as most radiotherapists accept its use and very fewwill tolerate in practice a higher dose. Many studies haveattempted to define the risk factors associated with chronicprogressive radiation myelopathy with differing conclusions.In the present paper the following main factors are discussedin detail: total dose, dose per fraction, length (volume) of thespinal cord irradiated segment of spinal cord and reirradiationof the cord to control the malignant disease. A number ofconclusions are obtained regarding the relative influence ofthese risk factors, particularly for the range of doses usuallygiven incidentally to the spinal cord in the treatment of tumorsin the region of the cord. It is obvious that the sample size inthe clinical studies is not adequate to define the multiple riskfactors of chronic progressive radiation myelopathy. In fact,the sample size required may be so large that the exact risksmay never be completely defined. It is unfortunate that thestandard of practice for limiting incidental dose to the spinalcord is determined more by litigation than by clinical judgment.Tumoricidal dose should never be compromised for thepurpose of limiting, where such liming forces even greaterprobability of compromising the tumoricidal dose.Tolerance of normal tissue to therapeutic irradiation.Int J Radiat Oncol Biol Phys. 1991 May 15;21(1):109-22Emami B, Lyman J, Brown A, Coia L, Goitein M,Munzenrider JE, Shank B, Solin LJ, WessonM.Mallinckrodt Institute of Radiology, WashingtonUniversity School of Medicine, St. Louis, MO 63110.The importance of knowledge on tolerance of normal tissueorgans to irradiation by radiation oncologists cannot beoveremphasized. Unfortunately, current knowledge is less than342