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J Korean Soc Ther Radiol > Volume 11(1); 1993 > Article
Journal of the Korean Society for Therapeutic Radiology 1993;11(1): 51-58.
Combined Effects of Gamma-irradiation and Hyperthermia on the Human Cell Lines for Various Temperatures and Time Sequences
Kyung Hwan Koh, Chul Koo Cho, Woo Yoon Park, Seong Yul Yoo, Hyong Geun Yun, Jae Won Shim, Mi Jung Lee
1Department of Therapeutic Radiology, Korea Cancer Center Hospital, Korea Cancer Center Hospital, Seoul, Korea.
2Department of Pediatric Oncology, Korea Cancer Center Hospital, Seoul, Korea.
We tried to establish the theoretical basis of clinical use of combined modality of hyperthermia and radiation therapy. For this purpose, we made an in vitro experiment in order to get the synergistic and/or additive effects on the cell killing of hyperthermia combined with radiation therapy by using the microwave-hyperthermia machine already installed at our department. In our experiment, we use two human cell lines: MKN-45(adenocarcinoma of stomach) and K-562(leukemia cell lines). In cases of combined treatments of hyperthermia and gamma-irradiation, the therapeutic effect was the highest in the simultaneous trial. Hyperthermia after gamma irradiation showed slightly higher therapeutic effect than that before irradiation without significant difference, but its effect was the same in the interval of 6 hours between hyperthermia and irradiation. The higher temperature and the longer treatment time were applied, the higher therapeutic effects were observed. We could observe the thermoresistance by time elapse at 43 degree C. When hyperthermia was done for 30 minutes at the same temperature, thermal enhancement ratio(TER) at D0.01(dose required surviving fraction of 0.01) were 2.5+/-0.08, 3.75+/-0.18, and 5.0+/-0.15 at 43 degree C, 44 degree C, and 45 degree C respectively in K-562 leukemia cell lines. Our experimental data showed that more cell killing effect can be obtained in the leukemia cell lines, although they usually are known to be radiosensitive, when treated with combined hyperthermia and radiation therapy. Furthermore, our data show that leukemia cell lines May have various intrinsic radiosensitivity, especially in vitro experiments. The magnitude of cell killing effect, however, will be less than that of MKN-45.
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