5 millimeters could be the difference between life and death for radiotherapy patients
A lung cancer patient’s chance of survival after radiotherapy could hinge on a matter of millimeters, researchers reported at the European Society for Radiotherapy and Oncology’s (ESTRO) 2018 conference in Barcelona.
Work led by Corinne Johnson, a medical physics PhD candidate at the Manchester Cancer Research Centre, found that for patients undergoing radiotherapy to treat lung or esophageal cancer, even the smallest of movements can make a sizable difference.
“We already know that using imaging can help us to target cancers much more precisely and make radiotherapy treatment more effective,” Johnson said in an ESTRO release. “This study examines how small differences in how a patient is lying can affect survival, even when an imaging protocol is used.”
Before radiotherapy, clinicians scan patients using CT and identify precisely where and how large a tumor is, as well as where to target any therapies. Still, radiotherapy comes with a host of harmful side effects, including an increased risk for heart disease.
Johnson and her colleagues studied 780 non-small cell lung cancer patients for their study, all of whom were treated with radiotherapy. As per the medical standard, each patient was imaged in the treatment machine prior to therapy to ensure they were laying within five millimeters of their original position.
The researchers found that when radiation dose was impacted—either by a patient or machine’s slight movements—so was that patient’s shot at survival. Those with slight radiation shifts toward their hearts were around 30 percent more likely to die than patients with similarly sized shifts geared away from their hearts.
The results were even more apparent in a subgroup of 177 esophageal cancer patients, who were 50 percent more likely to die if radiotherapy was directed even millimeters closer to their hearts.
Though their findings suggest troubling outcomes, Johnson and her colleagues said survival rates could likely be raised by tightening treatment guidelines and limiting patient movement.
“[This study] tells us that even very small remaining errors can have a major impact on patients’ survival chances, particularly when tumors are close to a vital organ like the heart,” Johnson said. “By imaging patients more frequently and by reducing the threshold on the accuracy of their position, we can help lower the dose of radiation that reaches the heart and avoid unnecessary damage.”
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.