Bursting Oxygen-loaded Microbubbles Near Solid Tumors Can Enhance Radiation Therapy

Scientists at Thomas Jefferson University in Philadelphia have developed a new technique to improve the effectiveness of radiation therapy for solid tumors. Their method employs nanotechnology in the form of oxygen-filled microbubbles that can be burst using focused ultrasound when they are near a tumor.

The majority of solid tumors are oxygen-deficient as they quickly outgrow their blood supply. This can make radiation therapy a challenge, as it works by creating oxygen radicals from oxygen present in tissues, which then go on to destroy the tissue. If the tissue is oxygen-deficient to begin with, fewer oxygen radicals are created, making the technique less effective.

This new technique aims to increase oxygen levels in solid tumors, making subsequent radiation therapy more effective. The research team turned to microbubbles – tiny gas-filled bubbles that can flow through blood vessels – as an oxygen delivery vehicle. After introducing the microbubbles to the blood flow through an intravenous injection, the team could “pop” them using a beam of ultrasound when they reached the site of the tumor, leading to increased oxygen levels in the tumor.

“The very act of bursting these microbubbles within the tumor tissue seems to change the local physiology of the tumor and make cells generally more permeable to oxygen and potentially to chemotherapy as well,” said John Eisenbrey, a researcher involved in the study. “We think this is a promising approach to test in patients to amplify the effects of radiation therapy.”

In animal tests, the researchers found that the delivered oxygen makes the tumors up to three times more sensitive to radiation therapy. Remarkably, the technique also nearly doubled the survival times in mice with solid tumors who received radiation therapy. Mice treated using oxygen-filled microbubbles survived for 76 days, whereas those treated using nitrogen-filled microbubbles survived for only 46 days.