Hyperthermic enhancement of tumour growth inhibition by accelerated carbon-ions in transplantable human esophageal cancer

Abstract

The study examined the effects of combination of hyperthermia (42d`C) and 290MeV/u carbon-ion (C—) beams or 200 kVp X-rays on tumour regrowth delay of transplantable human esophageal cancer as an in vivo model for radiotherapy of cancer. The C-beams were more effective in the tumour growth inhibition than X-rays. The relative biological effectiveness (RBE) of C-beams against X-rays was 2.00. It was observed that the interactive hyperthermic (42d`C, for 30 min) enhancement of tumour regrowth delay by high—linear energy transfer (LET) C-beams was similar to that of combination of low—LET X-rays with hyperthermia. The thermal enhancement ratios (TER) were 6.10 and 5.57 for X-rays and C-beams, respectively. These results suggest that hyperthermic treatment is effective in radiotherapy not only by low-LET radiation but also by high—LET radiation such as C-beams. In conclusion, the depression of the tumour growth by the combined treatment of hyperthermia (42d`C) and the C-beams strongly suggests the available possible application of interdisciplinary cancer therapy for refractory tumours.

Key Words:

• Carbon-ion beams
• hyperthermia
• TER
• esophageal cancer
• nude mice