title: In vitro cellular radiosensitivity in relationship to late normal tissue reactions in breast cancer patients: a multi-endpoint case-control study.
abstract: A minority of patients exhibits severe late normal tissue toxicity after radiotherapy (RT), possibly related to their inherent individual radiation sensitivity. This study aimed to evaluate four different candidate in vitro cellular radiosensitivity assays for prediction of late normal tissue reactions, in a retrospective matched case-control set-up of breast cancer patients.
  
  
  
  The study population consists of breast cancer patients expressing severe radiation toxicity (12 cases) and no or minimal reactions (12 controls), with a follow-up for at least 3 years. Late adverse reactions were evaluated by comparing standardized photographs pre- and post-RT resulting in an overall cosmetic score and by clinical examination using the LENT-SOMA scale. Four cellular assays on peripheral blood lymphocytes reported to be associated with normal tissue reactions were performed after in vitro irradiation of patient blood samples to compare case and control radiation responses: radiation-induced CD8+ late apoptosis, residual DNA double-strand breaks, G0 and G2 micronucleus assay.
  
  
  
  A significant difference was observed for all cellular endpoints when matched cases and controls were compared both pairwise and grouped. However, it is important to point out that most case-control pairs showed a substantial overlap in standard deviations, which questions the predictive value of the individual assays. The apoptosis assay performed best, with less apoptosis seen in CD8+ lymphocytes of the cases (average: 14.45%) than in their matched controls (average: 30.64%) for 11 out of 12 patient pairs (p < .01). The number of residual DNA DSB was higher in cases (average: 9.92 foci/cell) compared to their matched control patients (average: 9.17 foci/cell) (p < .01). The average dose response curve of the G0 MN assay for cases lies above the average dose response curve of the controls. Finally, a pairwise comparison of the G2 MN results showed a higher MN yield for cases (average: 351 MN/1000BN) compared to controls (average: 219 MN/1000BN) in 9 out of 10 pairs (p < .01).
  
  
  
  This matched case-control study in breast cancer patients, using different endpoints for in vitro cellular radiosensitivity related to DNA repair and apoptosis, suggests that patients' intrinsic radiosensitivity is involved in the development of late normal tissue reactions after RT. Larger prospective studies are warranted to validate the retrospective findings and to use in vitro cellular assays in the future to predict late normal tissue radiosensitivity and discriminate individuals with marked RT responses.
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.|b National Research Foundation (NRF) , iThemba LABS , Somerset West , South Africa.
authors: Charlot
authors: C
authors: Vandevoorde
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.
authors: Julie
authors: J
authors: Depuydt
authors: c Department of Radiotherapy , Ghent University Hospital , Ghent , Belgium.
authors: Liv
authors: L
authors: Veldeman
authors: c Department of Radiotherapy , Ghent University Hospital , Ghent , Belgium.
authors: Wilfried
authors: W
authors: De Neve
authors: d Radiation Protection Service , IISLAFE , Valencia , Spain.|e Grupo de Investigación Biomédica en Imagen GIBI230 , IISLAFE , Valencia , Spain.
authors: Natividad
authors: N
authors: Sebastià
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.|f Department of Pediatrics and Medical Genetics , Ghent University , Ghent , Belgium.
authors: Greet
authors: G
authors: Wieme
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.
authors: Annelot
authors: A
authors: Baert
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.
authors: Sofie
authors: S
authors: De Langhe
authors: g Department of Clinical Chemistry, Microbiology and Immunology , Ghent University , Ghent , Belgium.
authors: Jan
authors: J
authors: Philippé
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.
authors: Hubert
authors: H
authors: Thierens
authors: a Ghent University , Department of Basic Medical Sciences , Ghent , Belgium.
authors: Anne
authors: A
authors: Vral
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy*; D016022:Case-Control Studies; D004307:Dose-Response Relationship, Radiation; D023381:Endpoint Determination / Q000379:methods*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011832:Radiation Injuries / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology*; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: Apoptosis; DNA DSB repair; breast cancer; micronuclei; radiosensitivity; radiotherapy