Guidelines for Complications of Cancer Treatment Vol VIII Part B

Pseudo-progression needs to be differentiated from trueprogression.Radiation myelitisRadiation myelitis though rare is seen in brain tumour patientstreated with CSI or posterior fossa tumour.Higher probability of myelitis occurs with higher RTdose (>50Gy). Majority of acute radiation myeliis areself limiting. Late onset myelitis is permanent andassociated with significant neurodeficit.Radiation induced Optic neuropathy (RION)The optic chiasm is radiosensitive and blindness from damagewell documented. Risk of damage following RT is 1-2% withlatency period 2 months – 4 yrs. Gadolinium MR has definedthe injury due to injury to the vaso nervorum. Risk is relatedto dose and dose per fractionRMH experience: 411 patients, 1962-1986, 45-50Gy RT,visual deterioration, assumed to be RT induced, 1.5%(Brada et al., Clin Endo, ’93)University of Florida: 141 patients, 1965-1993, 45-55Gy,vision worse in 2% (McCord et al., IJROBP, ’97)PMH, 160 patients: 1972-1986, 40-50Gy, no visualdeterioration (Tsang et al., IJROBP, ’94). III rd to VI thnerves in the cavernous sinus exposed to a mean dose of14.2Gy (5 – 30Gy) and these had no new neuropathiesRadiation tolerance of structures to single fractiontreatment: Radiation related optic neuropathy was pickedup earliest by a delay or reduction in the amplitude ofvisual evoked potentials 15Gy: 77.8%354