Does the combination of hyperthermia with low LET (linear energy transfer) radiation induce anti-tumor effects equivalent to those seen with high LET radiation alone?. (1st January 2021)

• Record Type: Journal Article
• Authors: Elming, Pernille B.; Sørensen, Brita S.; Spejlborg, Harald; Overgaard, Jens; Horsman, Michael R.
• Is Part Of: International journal of hyperthermia. Volume 38:Number 1(2021)
• Page Start: 105
• Page End: 110
• Publication Date: 2021-01-01
• Subjects: Hyperthermia -- low LET radiation -- carbon ions -- C3H mammary carcinoma -- Local tumor control; Thermotherapy -- Periodicals; 615.832
• DOI: 10.1080/02656736.2021.1876929
• Languages: English
• ISSNs: 0265-6736

Abstract

Abstract: Introduction: The combination of hyperthermia with low LET (linear energy transfer) radiation may have similar anti-tumor effects as high LET radiation alone. This pre-clinical study determined the optimal heating temperature and time interval between radiation and heat to achieve this equivalent effect. Methods: C3H mammary carcinomas (200 mm 3 in size) growing in the right rear foot of CDF1 mice was used in all experiments. Tumors were locally irradiated with graded doses of either 240 kV ortho- or 6 MV mega-voltage X-rays to produce full dose-response curves. Heating (41.0–43.5 °C; 60 min) was achieved by immersing the tumor bearing foot in a water-bath applied at the same time, or up to 4-hours after, irradiating. The endpoint was the percentage of mice showing local tumor control at 90 days, with enhancements calculated from the ratios of the radiation doses causing 50% tumor control (± 95% confidence intervals). Results: Previous published results in this tumor model reported that carbon ions were 1.3–1.7 times more effective than low LET radiation at inducing tumor control. Similar enhancements occurred with a temperature of only 41.0 °C with a simultaneous heat and radiation treatment. However, higher temperatures were needed with the introduction of any interval; at 42.5 °C, the enhancement was 2.5 with a simultaneous treatment, decreasing to a value within the carbon ion range with a 4-hour interval. Conclusions: Combining hyperthermia with low LET radiation can be as effective as high LET at inducing tumor control, but the temperature needed depended on the time interval between the two modalities.