In many past clinical studies in which hyperthermia enhanced the efficacy of radiotherapy, the tumor temperatures could be raised only to 40-42°C range in most cases. The heat-induced cell death, cellular radiosensitization, and vascular damage induced by such mild temperature hyperthermia (MTH) are likely to be insignificant despite the increased response of tumors to radiotherapy. Heating rodent tumors at 40-42°C was found to cause an enduring increase in blood flow and oxygenation in the tumors. Recent studies with canine soft tissue sarcoma and human tumor clinical studies also demonstrated that MTH improves tumor oxygenation, and enhances response of the tumors to radiotherapy or chemoradiotherapy. The increased blood flow and vascular permeability caused by MTH may also improve the delivery of various therapeutic agents such as chemotherapy drugs, immunotherapeutic agents and genetic constructs for gene therapy to tumor cells. MTH as a means to potentiate the efficacy of radiotherapy and others warrants further investigation.
Bibliographical noteFunding Information:
The technical assistance of Mr Brent Williams is gratefully acknowledged. This work was supported by grant CA44114 from the NIH/NCI, and National R&D Program for Cancer Control, Ministry of Health & Welfare, Republic of Korea (0320300-2) and 2003 KISTEP & MOST, Korean Government through its National Nuclear Technology Program.
- Blood flow
- Mild temperature hyperthermia
- Tumor oxygenation
- Tumor pO