Hyperthermia is being studied as a potential cancer treatment. Heating cells up to 113 degrees appears to weaken or destroy tumor cells in some patients.
Numerous clinical trials have studied hyperthermia in combination with radiation therapy and/or chemotherapy. Many of these studies, but not all, have shown a significant reduction in tumor size when hyperthermia is combined with other treatments (National Cancer Institute website, accessed July 2007).
Researchers at Charité-Universitätsmedizin in Berlin, Germany have developed a new way to focus tumor killing heat treatment on the prostate gland. Using futuristic techniques, doctors inject metallic nanoparticles into the prostate gland. A magnetic field then excites the particles causing them to heat the surrounding tissue to temperatures as high as 113 degrees F and destroy the tumor. The therapy also produced a decline in prostate specific antigen levels that lasted an average of 4.5 months after therapy.
Cancerous tumors are more sensitive to heat damage because they lack efficient ways to dissipate the heat. Heat also increases oxygen levels within tumors and oxygen in turn helps to naturally suppress tumor growth through a master gene switch called HIF-1 alpha. Used alone, hyperthermia is effective in shrinking tumors located close to the skin. One such study published in the Annals of Surgical Oncology showed significant tumor size reduction and tumor cell kill in 8 (80%) of 10 breast cancer patients.
"Hyperthermia boosts the killing power of radiation and chemotherapy by up to 10 times greater than without heat," says researcher Mark Dewhirst in a Duke University press release. Heating tumors before radiation treatment has been shown to shrink the tumors completely in more patients than radiation treatment alone, according to a study by Duke Comprehensive Cancer Center radiation oncologists. The study found that combined therapy shrank tumors completely in 66 percent of patients with cancers in the breast, chest wall, head and neck, and skin (melanoma). By contrast, radiation alone caused full tumor shrinkage in 42 percent of patients.
Most normal tissues are not damaged during hyperthermia if the temperature remains under 111°F. However, due to differences in tissue density, higher temperatures may occur in various spots. This can result in burns, blisters, discomfort, or pain. Most side effects are temporary. Whole-body hyperthermia can cause more serious side effects, including cardiac and vascular disorders, but these effects are uncommon. Diarrhea, nausea, and vomiting are commonly observed after whole-body hyperthermia.
Although hyperthermia is clearly an effective treatment option, variations in instrumentation and clinical study techniques has slowed hyperthermia’s widespread use as a stand alone method of care.
Hyperthermia Glossary
Whole Body Hyperthermia raises body temperature above normal. Though it does not directly kill tumor cells, it can be used along with chemotherapy to increase its effectiveness.
External heat treatment uses applicators positioned around or near the appropriate region, and energy is focused on the tumor to raise its temperature.
Intraluminal or endocavitary methods may be used to treat tumors within or near body cavities, such as the esophagus or rectum. Probes are placed inside the cavity and inserted into the tumor to deliver energy and directly heat the area.
Interstitial techniques are used to treat tumors deep within the body, such as brain tumors. This technique allows the tumor to be heated to higher temperatures than external techniques. Under anesthesia, probes or needles are inserted into the tumor while imaging, such as ultrasound, CT or MRI, may be used for proper probe positioning inside the tumor. The heat source may then be inserted into the probe.
Radiofrequency ablation (RFA) is a type of interstitial hyperthermia that uses radio waves to heat and kill cancer cells.
Magnetic thermal ablation uses metallic nanoparticles (biocompatible superparamagnetic nanoparticles) which are excited to produce heat by an external magnetic source.
References:
- Annals of Surgical Oncology. 2002. 9(4):326-332.
- Cell Cycle. 2004. 3(8):1027-9.
- Int J Hyperthermia. 2007 May;23(3):315-23.
- J Clin Oncol. 2005 May 1;23(13):3079-85.
- J Natl Compr Canc Netw. 2007 Mar;5(3):345-8.
- Prostate. 2005; 64: 283–292.
- The Oncologist. 2004. 9(suppl 5): 10 – 17.
- Harnessing Fat to Attack Cancer 1/2/2007 Duke Press release.
4/28/05. Duke Press release.
Posted July 2007
