Prediction of scattered dose to the testes in abdominopelvic radiotherapy

Radical abdominal radiotherapy in men runs the risk of impairing their fert ility owing to scattered dose to the testes, outside of the treated volume. In patients for whom this is a concern it is important to be able to predi ct the dose to the testes before treatment in order to determine whether se men cryopreservation should be undertaken and testicular shielding performe d during treatment. Measurements have been made on an anthropomorphic phant om to determine the magnitude of these doses for a four-field treatment con sisting of an anterior-posterior parallel pair and a lateral parallel pair. A dataset is presented, which, together with a correction for patient size , allows an estimate of testicular dose to be made given only the photon en ergy, interfield distances and the distance from the testes to the nearest beam edge. Thermoluminescent dosimetry has been carried out in 17 patients to validate the use of the data tables. The results indicate that testicula r doses may be estimated with a standard deviation corresponding to 1%-2% o f the tumour dose, which is sufficient for the purpose of determining wheth er fertility is threatened by a planned treatment.