The amount of radiation it takes to kill a tumor depends on the level of oxygen in the tumor cells. This can vary greatly, but oncologists don’t currently adjust radiation doses to account for it. Gregory Ekchian, cofounder of Stratagen Bio, has developed a sensor for reading tumor oxygen levels to personalize cancer treatment.
Ekchian recognized a glaring need for a new sensing tool after discussions with clinicians at Brigham and Women’s Hospital in Boston. He developed a prototype for a cancer treatment technique called high-dose-rate brachytherapy. In this form of treatment, doctors puncture the tumor with a series of hollow catheter tubes and then drop radioactive seeds through the tubes to suffuse the tumor with radiation, removing them once the desired dose has been delivered.
For his prototype, Ekchian added a strip of a recently invented oxygen-sensitive polymer to the tips of a modified version of the catheters. During routine MRI scans, protons in the polymer are excited; these protons return to equilibrium far faster in catheters surrounded by high levels of oxygen than low levels. The speed at which they return to equilibrium can therefore be used to map out how oxygen levels vary in different parts of the tumor, allowing oncologists to pinpoint where radiation doses should go and tailor their length and intensity to be most effective.
“If we weren’t worried about healthy tissue, we would just boost the dose to the entire tumor,” he says, but excess radiation can harm the patient. That means “it’s really important to figure out where those high doses need to go.”
Ekchian is preparing to publish the results of a clinical trial involving seven patients with cervical cancer, the first in humans. He ultimately hopes to employ his oxygen-sensing applications for a wide range of clinical needs.