title: Radiation therapy for stage IIA and IIB testicular seminoma: peripheral dose calculations and risk assessments.
abstract: This study was conducted to calculate the peripheral dose to critical structures and assess the radiation risks from modern radiotherapy for stage IIA/IIB testicular seminoma. A Monte Carlo code was used for treatment simulation on a computational phantom representing an average adult. The initial treatment phase involved anteroposterior and posteroanaterior modified dog-leg fields exposing para-aortic and ipsilateral iliac lymph nodes followed by a cone-down phase for nodal mass irradiation. Peripheral doses were calculated using different modified dog-leg field dimensions and an extended conventional dog-leg portal. The risk models of the BEIR-VII report and ICRP-103 were combined with dosimetric calculations to estimate the probability of developing stochastic effects. Radiotherapy for stage IIA seminoma with a target dose of 30 Gy resulted in a range of 23.0-603.7 mGy to non-targeted peripheral tissues and organs. The corresponding range for treatment of stage IIB disease to a cumulative dose of 36 Gy was 24.2-633.9 mGy. A dose variation of less than 13% was found by altering the field dimensions. Radiotherapy with the conventional instead of the modern modified dog-leg field increased the peripheral dose up to 8.2 times. The calculated heart doses of 589.0-632.9 mGy may increase the risk for developing cardiovascular diseases whereas the testicular dose of more than 231.9 mGy may lead to a temporary infertility. The probability of birth abnormalities in the offspring of cancer survivors was below 0.13% which is much lower than the spontaneous mutation rate. Abdominoplevic irradiation may increase the lifetime intrinsic risk for the induction of secondary malignancies by 0.6-3.9% depending upon the site of interest, patient's age and tumor dose. Radiotherapy for stage IIA/IIB seminoma with restricted fields and low doses is associated with an increased morbidity. These data may allow the definition of a risk-adapted follow-up scheme for long-term testicular cancer survivors.
authors.affiliation: Department of Medical Physics, Faculty of Medicine, University of Crete, PO Box 2208, 71003 Iraklion, Crete, Greece.
authors.forename: Michalis
authors.initials: M
authors.lastname: Mazonakis
authors.forename: Theocharris
authors.initials: T
authors.lastname: Berris
authors.forename: Efrossyni
authors.initials: E
authors.lastname: Lyraraki
authors.forename: John
authors.initials: J
authors.lastname: Damilakis
mesh_terms: D000328:Adult; D000465:Algorithms; D006801:Humans; D008297:Male; D011829:Radiation Dosage; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D018570:Risk Assessment; D018239:Seminoma / Q000473:pathology / Q000532:radiotherapy*; D013736:Testicular Neoplasms / Q000473:pathology / Q000532:radiotherapy*