Microbubbles Could Make Breast Cancer More Susceptible to Radiation Therapy

Bursting oxygen-filled microbubbles could make breast tumors three times more sensitive to radiation therapy in preliminary tests.

A new approach, oxygen-filled microbubbles, could help boost the effects of radiation therapy and extend survival in animal models of breast cancer. The preliminary study makes a strong case for moving this novel approach into clinical trials with breast cancer patients.

Microbubbles are usually used to help improve the picture on ultrasound imaging scans. Recently, scientists have begun to test whether the same technology could be useful for treating cancer.

Most solid tumors, like breast cancer, become starved of oxygen, in part because they outgrow the supply of oxygen-carrying blood vessels that penetrate the tumor mass. That lack of oxygen also makes solid tumors more resistant to radiation treatment. Enter microbubbles. By injecting oxygen-filled microbubbles, and then popping them with ultrasound prior to radiation treatment, the researchers infuse the tumors with oxygen, making the cells much more sensitive to the radiation.

“Finding a way to reverse oxygen deficiency in tumors has been a goal in radiation therapy for over 50 years,” says senior author Dr. John Eisenbrey, assistant Professor and investigator at Jefferson’s Sidney Kimmel Cancer Center. “We’ve demonstrated here that oxygen microbubbles flush tumors with the gas and make radiation therapy significantly more effective in animal models.”

In the study, Dr. Eisenbrey and colleagues showed that popping the microbubble with ultrasound immediately prior to radiation treatment could triple the sensitivity of the cancer to radiation.  It also nearly doubled the survival times in mice from 46 days with placebo, nitrogen-filled microbubbles, to 76 days with oxygen-filled microbubbles.

In fact, Dr. Eisenbrey and colleagues at the Sidney Kimmel Cancer Center are currently using a similar approach in a first-in-human clinical trial of microbubbles for liver cancer (Clinicaltrials.gov number: NCT03199274). The researcher are bursting microbubbles in patients with liver cancer in combination with their standard treatment of radioembolization therapy. Though not filled with oxygen, the microbubble popping is thought to disrupt the tumor enough to offer therapeutic benefit over radioembolization alone.

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