Biological rationale and clinical experience with hyperthermia

Area of Science:

• Oncology
• Radiation Oncology
• Medical Physics

Background:

• Hyperthermia (HT) is increasingly studied as an adjunct to radiation therapy (RT) for cancer management.
• Numerous studies have assessed HT efficacy, especially for superficially located tumors, focusing on locoregional control.
• Tumor physiology, including acidosis and hypoxia, can enhance HT's cytotoxic effects and sensitivity to heat.

Purpose of the Study:

• To evaluate the efficacy of hyperthermia as an adjunct to radiation therapy in cancer treatment.
• To identify key prognostic factors influencing complete response and local control in patients receiving HT and RT.
• To review the impact of HT on thermal enhancement ratios and treatment outcomes in specific cancer types.

Main Methods:

• Review of randomized and non-randomized studies on HT combined with RT or chemotherapy.
• Analysis of clinical investigations in breast lesions, melanoma, and head and neck neoplasms.
• Assessment of prognostic factors including RT dose, tumor size, thermal parameters (t43min, Tmin, T90), tumor histology, and depth.

Main Results:

• HT significantly impacts locoregional tumor control, with thermal enhancement ratios of 1.4 for neck nodes, 1.5 for breast, and 2 for melanoma.
• Prognostic factors for complete response include RT dose, tumor size, and thermal parameters (t43min, Tmin, T90).
• Factors influencing local control duration include tumor histology, RT dose, tumor depth, and Tmin. The number of HT fractions appears less critical than adequate thermal dose delivery.

Conclusions:

• Hyperthermia demonstrates potential in improving complete response rates and local control when used with radiation therapy.
• Optimal outcomes are linked to specific RT doses, tumor characteristics, and precise thermal delivery.
• Further validation through multi-institutional randomized clinical trials is essential to confirm HT's efficacy as an adjunct to RT.