Renal tolerance to nonhomogenous irradiation: comparison of observed effects to predictions of normal tissue complication probability from different biophysical models.
OBJECTIVE
A patient series was analyzed retrospectively as an example of whole organ kidney irradiation with an inhomogenous dose distribution to test the validity of biophysical models predicting normal tissue tolerance to radiotherapy.


METHODS
From 1969 to 1984, 142 patients with seminoma were irradiated to the paraaortic region using predominantly rotational techniques which led to variable but partly substantial exposure of the kidneys. Median follow up was 8.2 (2.1-21) years and actuarial 10-year survival (Kaplan-Meier estimate) 82.8%. For all patients 3-dimensional dose distributions were reconstructed and normal tissue complication probabilities for the kidneys were generated from the individual dose volume histograms. To this respect different published biophysical algorithms had been introduced in a 3-dimensional-treatment planning system.


RESULTS
In seven patients clinical manifest renal impairment was observed (interval 10-84 months). An excellent agreement between predicted and observed effects was seen for two volume-oriented models, whereas complications were overestimated by an algorithm based on critical element assumptions.


CONCLUSIONS
Should these observations be confirmed and extended to different types of organs corresponding algorithms could easily be integrated into 3-dimensional-treatment planning programs and be used for comparing and judging different plans on a more biologically oriented basis.
Flentje
M
M
Dept. of Radiology, University of Heidelberg, Germany.
Hensley
F
F
Gademann
G
G
Menke
M
M
Wannenmacher
M
M
D000328:Adult; D000368:Aged; D003964:Diaphragm; D004407:Dysgerminoma / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007668:Kidney / Q000528:radiation effects*; D008198:Lymph Nodes / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009367:Neoplasm Staging; D011336:Probability; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D013736:Testicular Neoplasms / Q000473:pathology / Q000532:radiotherapy*