Intrinsic radiosensitivity of head and neck carcinomas as predictive test for clinical tumor control: Comparative analysis and critical assessment of technical reliability

Abstract

AbstractUsing a cell adhesion matrix monolayer culture system, we assayed the intrinsic radiosensitivity of 108 biopsies or surgical specimens of head and neck, colo‐rectum, or cervix uteri carcinomas. After irradiating single cell suspensions with increasing doses (0–4 Gy), surviving fractions at 2 Gy (SF‐2), initial slope α were estimated after a linear quadratic fitting of the curves. For cultures from biopsies or surgical specimens of head and neck carcinomas, the overall success rate was 65%. The pattern of the causes of failure for mass cultures was similar in other institutions investigating intrinsic radiosensitivity of squamous cell carcinomas. Within the same anatomic site and histological type, rumors were characterized by a wide range of in vitro radiosensitivity. In a series of 28 patients with head and neck cancers, the mean and standard deviation values of SF‐2 were 0.30 ± 0.34. Likewise, α coefficients had an average of 0.61 ± 0.96 Gy−1. Cultures from colo‐rectal cancers seem to have a higher mean level of intrinsic radioresistance (mean SF‐2 = 0.49) than that of cells from head and neck tumors. Papanicolaou (PAP) staining and immuno‐chemistry studies using monoclonal antibodies showed that stromal expression was a major problem for techniques using pre‐coated plates. Nevertheless, the pattern of cumulative distribution of SF‐2 values is not significantly different for cultures characterized by fibroblast overgrowth. In conclusion, notwithstanding variations in fibroblast growth, the comparative analysis of data published so far on intrinsic radiosensitivity shows that similar distributions of individual survival parameter values are yielded in the laboratories involved in this research field. Nevertheless, further studies on culture characterization, using monoclonal antibodies and flow cytometry, should be carried out to quantify better the impact of fibroblast contamination on culture response to irradiation. © Wiley‐Liss, Inc.