Effect of dose and dose-distribution in damage to the kidney following abdominal radiotherapy.

PURPOSE: To define the effects of abdominal radiotherapy on the kidney with regard to dose-distribution parameters.
MATERIALS AND METHODS: Ninety-one patients with abdominal radiotherapy were included in the study, and the minimum follow-up was 1 year. Conventional fractionation, 5 x 1.8-2.0 Gy week(-1) to total doses of 30.6-62.5 Gy, was employed. Assessment of organ function was performed before, immediately after, and at 6 months and 1 year after radiotherapy. In cases with a significant radiation response at 1 year, subsequent follow-ups were done at 6-month intervals. Documented parameters included clinical examination, static and sequential scintigraphy of the kidneys, abdominal computed tomography, and sonography.
RESULTS: Twenty-one patients (23%) developed a reduction in kidney function detected by static scintigraphy. Only in 15 of these patients was impairment of renal function observed by sequential scintigraphy. The contribution of the irradiated kidney to overall renal function decreased progressively to 34-40% by the third year after treatment. Hypertension was seen in two patients. No changes were found in laboratory parameters. ED(50) for scintigraphic changes decreased from 27 Gy for 10% of the volume to 7.6 Gy for 100%. ED(5) were in the range of 3-6 Gy, and this was independent of volume.
CONCLUSIONS: Sophisticated imaging techniques allow the identification of radiation effects in partial volumes of the kidneys. A dose-response relationship in relation to the volume of kidney irradiated can thus be established for scintigraphic changes. As in a number of other organs, such changes do not relate directly to loss of renal function due to the reserve capacity of unirradiated kidney tissue.