Radiosensitization
Similar to sensitization to chemotherapy, tumors can be made more receptive to radiotherapy through local hyperthermia1.
Hyperthermia triggers an increased flow of blood and delivery of oxygen to a tumor, enhancing the rate of its metabolic processes, which increases the efficacy of radiotherapy, especially in cases where the tumor tissue is hypoxic2,3. Sensitized tumors require a reduced radiation dose in order to induce cell death, which mitigates the side effects of radiotherapy4,5.
Conventional methods for inducing sensitization to radiotherapy are the same as those used in the sensitization to chemotherapy processes, and thus focused ultrasound provides the advantage of being a non-invasive, local, and non-ionizing method of inducing hyperthermia4. In tumors where radiation therapy is a viable treatment option, focused ultrasound could be used as a neo-adjuvant to reduce the radiation dose needed to kill the cancer cells. The toxic effects of radiation accumulate in the body with each treatment, so reducing the dose needed in a single treatment affords the patient the ability to undergo additional radiation treatments later in their life if necessary6.
References:
[1] D. S. Finley, F. Pouliot, B. Shuch, A. Chin, A. Pantuck, J. B. Dekernion, and A. S. Belldegrun, “Ultrasound-based combination therapy: potential in urologic cancer.,” Expert Rev. Anticancer. Ther., vol. 11, no. 1, pp. 107–113, Jan. 2011.
[2] Song CW, Shakil A, Osborn JL, Iwata K. Tumour oxygenation is increased by hyperthermia at mild temperatures. Int. J. Hyperth. Off. J. Eur. Soc. Hyperthermic Oncol. North Am. Hyperth. Group. 1996;12:367–73.
[3] Rao W, Deng Z-S, Liu J. A review of hyperthermia combined with radiotherapy/chemotherapy on malignant tumors. Crit. Rev. Biomed. Eng. 2010;38:101–16.
[4] Wang S, Zderic V, Frenkel V. Extracorporeal, low-energy focused ultrasound for noninvasive and nondestructive targeted hyperthermia. Future Oncol. Lond. Engl. 2010;6:1497–511.
[5] H. H. Kampinga, “Cell biological effects of hyperthermia alone or combined with radiation or drugs: a short introduction to newcomers in the field.,” Int. J. Hyperth. : Off. J. Eur. Soc. Hyperthermic Oncol. North Am. Hyperth. Group, vol. 22, no. 3, pp. 191–196, May 2006.
[6] Understanding Radiation Therapy: A Guide for Patients and Families. American Cancer Society. 2014.