Radiation Tolerance of the Lower Urinary Tract
Emami et al.63 pooled data from a number of studies utilizing radiation to treat pelvic malignancies, and reported the bladder TD 5/5 (5% severe late toxicity at 5 years) is 65 Gy for irradiation of a contracted whole bladder, versus 80 Gy for irradiation of two thirds of the bladder. TD 50/5 was estimated to be 80 Gy. This study did not utilize 3D imaging and it is argued that with advances in radiation technique, the actual TD 5/5 to the bladder may be higher.
A similar study done by Marks et al. estimated bladder toxicity based on literature reviews of prostate, bladder, and cervical cancers.41 Incidence of grades 3 to 4 toxicity and dose-volume relationships after external beam radiation therapy and BT were estimated (Table 32.3) Marks et al. estimated a clinical complication rate of approximately 5% to 10% with a whole bladder dose of 50 Gy, and higher complication rates with doses of 50 to 65 Gy. Thus, whole bladder irradiation to >50 Gy in 2-Gy fractions was associated with significant risk of bladder dysfunction.
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