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MO‐D‐T‐6E‐06: In Vitro Measurement of the Repair Time for Prostate Cancer
Author(s) -
Wang J,
Rhee J,
Stewart R,
Li X
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1998276
Subject(s) - prostate cancer , medicine , prostate , nuclear medicine , cancer , urology , confidence interval
Purpose: It is concerned that the prolonged delivery time of IMRT may affect the treatment effectiveness. For prostate cancer, biological modeling suggests that the effectiveness of IMRT could be degraded by over 10% when the repair half‐time is short compared to the fraction delivery time. Published data show that repair half‐time for prostate cancer may be as short as 10 minutes or as long as a few hours. The purpose of this study is to measure the repair half‐time of prostate cancer cells with split‐dose experiments in vitro . Method and Materials: We performed a series of single‐fraction and split‐dose experiments with the DU‐145 cell line, which is derived from human prostate cancer, and analyzed the data using the linear‐quadratic (LQ) model. The study is presented in two parts: (1) estimate the LQ parameters (α and α/β)from high‐dose‐rate survival data (0 to 12 Gy) and (2) determine the repair half‐time from split‐dose experiments (4 Gy + 4 Gy and 6 Gy + 6 Gy) with time intervals ranging from 6 minutes to 8 hours. Results: Preliminary analysis of our pilot data shows that DU‐145 cells are very radiosensitive with a large α/β ratio (α = 0.52 Gy −1 and α/β = 11.5 Gy). The repair half‐time derived from the split‐dose data is 18 minutes and the estimated standard confidence interval is between 16 to 19 minutes. No component of repair half‐time over one hour has been detected. Conclusion: The sublethal damage repair of DU‐145 prostate cancer cells is very rapid with a repair half‐time less than 20 minutes, which is consistent to the repair half‐time of 16 minutes derived from clinical data in a previously reported study. Our preliminary results needs to be verified in the follow‐up experiments.