Chemotherapy remains a blunt instrument in the fight against cancer. However, by combining chemotherapy with sound waves, researchers have found a way to turn chemotherapy into a scalpel rather than a stick, thus avoiding damage to nearby tissue and the entire body.
Although the methods doctors use to fight cancer are rapidly increasing, traditional chemotherapy is still widely used to fight tumors. In fact, a study in The Lancet Oncology predicts that the number of people needing chemotherapy will increase by 53% between 2018 and 2040. But well-known problems with chemotherapy remain: chemotherapy can cause hair loss, nausea, weight loss, anemia, peripheral neuropathy, and more. In addition, because chemotherapy drugs treat the whole body, they can cause damage to cells other than the tumor target.
To make chemotherapy more targeted, in 2020 researchers combined anti-cancer chemicals with lasers to activate the chemicals at the tumor site. While the treatment is promising, its effectiveness is limited to a few millimeters under the skin, which is the maximum depth that the laser beam-activated chemicals can penetrate.
Scientists at the City University of Hong Kong (City University) were trying to take advantage of the targeted activation function of chemotherapy drugs but also increase the depth of their effects, so they thought of using sound waves.
Researchers used cancer cell cultures in the laboratory to create a small-molecule platinum drug called cyanoplatin and concentrated it at the tumor site. The original drug is a compound that is inert until activated in the body. They then irradiated the cyanoplatin with highly targeted ultrasound waves, converting it into carboplatin, a common chemotherapy drug. This induces tumor death by damaging mitochondria within cancer cells.
This method reduced the survival rate of cancer cells by 51 percent when the tissue was covered by 1 centimeter (about 0.4 inches), and by 33 percent when the tissue was covered by 2 centimeters.
Further testing in mice showed that this approach was able to completely eliminate two tumors and significantly inhibit the growth of other tumors after six days of treatment.
"Our carefully designed functional ultrasound enables sonosensitization chemotherapy to be a precise tumor-specific treatment with good penetration properties," said study co-author Zhu Guangyu from CityU's Department of Chemistry. "More importantly, our system can focus ultrasound on a specific area within 8 millimeters, thereby highly concentrating ultrasound energy in a tiny area and activating the phonon-reactive original drug, providing an efficient method with minimal side effects."
Additionally, because cyanoplatin fluoresces, the researchers found that their method could also be used as an imaging system that could map tumors in three dimensions, precisely guide drug particles, and monitor drug accumulation in tumors in real time.
The research results have been published in the journal Science Advances.