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These results indicate that the analysis of translocations using FISH after in vitro irradiation correlates with clinical response to radiation. This cytogenetic assay should be considered as a potential predictor of radiosensitivity.

A simple in vitro alpha radiation exposure system (ARES) was designed to study the biological effects of alpha particle radiation. The ARES consists of six (241)Am electroplated stainless steel discs with activities averaging 66 kBq and Mylar-based culture dishes to allow the transmission of alpha particles. The dosimetry of the exposure system was calculated using the GEANT4 Monte Carlo simulation toolkit with the source code adapted from the open-source Microbeam example. The average dose rate and linear energy transfer of the system was simulated to be 0.98 ± 0.01 (statistical)(+0.18)( - 0.00) (systematic) Gy h(-1) and 127.4 ± 0.4 (statistical)(+23)( - 0) (systematic) keV µm(-1), respectively. The system was characterized by a comparison of the survival curves of gamma and alpha irradiated cell lines which showed a relative biological effectiveness of 6.3. This is in good agreement with values obtained using other published alpha particle exposure systems. Results show that the ARES provides a simple, cost-effective exposure platform for research into the biological effects of alpha particle radiation using in vitro modelling of cell cultures.

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Background and Purpose. This project examined the in vitro   γH2AX response in lymphocytes of prostate cancer patients who had a radiosensitive response after receiving radiotherapy. The goal of this project was to determine whether the γH2AX response, as measured by flow cytometry, could be used as a marker of individual patient radiosensitivity. Materials and Methods. Patients were selected from a randomized clinical trial evaluating the optimal timing of Dose Escalated Radiation and short-course Androgen Deprivation Therapy. Of 438 patients, 3% developed Grade 3 late radiation proctitis and were considered to be radiosensitive. Blood was drawn from 10 of these patients along with 20 matched samples from patients with Grade 0 proctitis. Dose response curves up to 10 Gy along with time response curves after 2 Gy (0–24 h) were generated for each sample. The γH2AX response in lymphocytes and lymphocyte subsets was analyzed by flow cytometry. Results. There were no significant differences between the radiosensitive and control samples for either the dose course or the time course. Conclusions. Although γH2AX response has previously been demonstrated to be an indicator of individual patient radiosensitivity, flow cytometry lacks the sensitivity necessary to distinguish any differences between samples from control and radiosensitive patients.