Oxygen Decelerates Many Tumors When Combined with Radiation Therapy
A multidisciplinary team at UT Southwestern Medical Center has found that measuring the oxygenation of tumors can be a valuable tool in guiding radiation therapy, opening the door for personalized therapies that keep tumors in check with oxygen enhancement.
In a study examining tissue oxygenation levels and predicting radiation response in rat prostate tumors, Ralph Mason, PhD, Professor of Radiology and Director of the Cancer Imaging Program at UT Southwestern, and colleagues found that countering hypoxic and aggressive tumors with an “oxygen challenge”—inhaling oxygen while monitoring tumor response—coincided with a greater delay in tumor growth in this irradiated animal model. The findings were published online in Magnetic Resonance in Medicine.
Effect of Oxygenation on Tumor Growth
Over the past several years, research conducted by Dr. Mason and colleagues has been building on findings that demonstrate that hypoxic conditions actually stimulate tumor angiogenesis and lead to metastasis and genetic instability in cancer. The theory follows that breathing oxygen or enriching the oxygen content of hypoxic cancer tissues improves therapy.
In the current study, smaller tumors were found to be significantly better oxygenated than larger tumors based on magnetic resonance imaging. This confirmed previous investigations that showed a range of hypoxic environments depending on the size of the tumor.
Findings May Lead to Personalized Therapies
“The next step is clinical trials to assess tumor response to radiation therapy,” said Dr. Mason. “Tumors determined to be hypoxic can be evaluated and made responsive through mild and easy-to-administer interventions, such as breathing more oxygen or taking a vasoactive drug. Monitoring the response to oxygen breathing tells us which tumors will benefit.”
If the results are confirmed in humans, the implications for personalized therapies for other cancers could mean fewer radiation treatments, or, ideally, one single high-dose treatment.
“The ability to stratify tumors based on hypoxia offers new opportunities to tailor therapy to tumor characteristics, potentially enhancing success through personalized medicine,” Dr. Mason said.
Dr. Mason’s team has worked to understand how low oxygen concentration can cause radiation resistance in tumors. In some cases, the simple addition of oxygen to stereotactic body radiation greatly improves response. The key is to identify those patients who will benefit. Clinical trials are underway to assess the effectiveness of oxygenation during treatment with stereotactic body radiation in humans.
The study was supported by the National Cancer Institute.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
