Clonogenic survival and cytokinesis-blocked binucleation of skin fibroblasts and normal tissue complications in soft tissue sarcoma patients treated with preoperative radiotherapy

Abstract

Background and purposeTo evaluate the clonogenic and cytokinesis-blocked assays in skin fibroblast cultures for their utility as tools for predicting normal tissue responses in soft tissue sarcoma (STS) patients treated with preoperative radiotherapy. Patients and methodsDermal fibroblast strains were established from skin biopsies of 26 STS patients who received preoperative radiotherapy. Cultures were subjected to the colony forming and cytokinesis-blocked assays after low (∼0.02Gy/min) dose-rate 60Co γ-irradiation. Fibroblast radiosensitivity was expressed as the dose for 1% clonogenic survival, D0.01, based on colonies/clusters with ≥10 cells. Fibroblast proliferative capability was represented by binucleation index (BNI) and genomic damage was expressed in terms of micronucleus frequency. Wound healing complications (WHC) and subcutaneous fibrosis were the clinical endpoints examined. The ability of each in vitro parameter to detect patients at high risk of a given normal tissue complication was assessed using receiver operating characteristic (ROC) analysis. ResultsWhile fibroblasts from patients without WHC were marginally more radiosensitive than fibroblasts from patients with WHC (P=0.08), the reduction in BNI following a dose of 2.4Gy was significantly higher in strains from patients without WHC compared to those from patients with WHC (P=0.01). The area under the ROC curve (c-index) is indicative of the power of discrimination of D0.01 and BNI for WHC, and was found to be 0.68 and 0.79, respectively. Subcutaneous fibrosis was not associated with D0.01 (rs=0.09, P=0.66) and the percent reduction in BNI after 2.4Gy (rs=−0.19, P=0.36). Micronucleus frequency did not reflect differences in normal tissue responses. ConclusionThese data suggest that it is the ability of fibroblasts to undergo one–three divisions in vitro following radiation treatment that may reflect the development of wound healing morbidity or subcutaneous fibrosis in this population of patients.