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Medical Rounds

Personalizing Radiation Therapy

Radiation therapy is a mainstay in the arsenal of treatments to fight cancer. But it can take several weeks of treatment before doctors know whether it’s working, and in some patients the therapy isn’t effective at all.

A new Johns Hopkins study offers the promise of using noninvasive methods of examining changes in cancerous tumors to determine whether they’ll respond to radiation treatment before treatment even begins. The findings can potentially help identify subsets of patients who are best suited for radiation treatment, thereby reducing medical overtreatment and helping some patients avoid the adverse effects of radiation.

“If we knew in advance that the patient’s tumor is resistant, appropriate changes to the treatment plan, such as escalation of radiation doses, can be implemented. On the other hand, if a tumor is found to be more sensitive, the dose may be adjusted to a level that would still control the tumor but greatly reduce the risk of normal tissue complications,” says biomedical engineer Ishan Barman, senior author of the study, which was published in Cancer Research.

In typical radiation therapy, small doses of radiation are delivered over a period of five to seven weeks. There’s currently no definitive way to predict treatment response before therapy or even in the early weeks of therapy. The earliest clinicians can examine tumor shrinkage is two to three weeks after therapy, using computed tomography and MRI scans.

While other studies have investigated molecular changes in tumors as a way to pre-emptively identify tumors that won’t respond to radiation treatment, Barman’s team says its research is unique. Team members studied multiple types of cancers (including head and neck, and lung cancer) and used smaller doses of radiation, which more accurately reflects current radiation therapy practices.

“Previous researchers used a single large dose of radiation, resulting in biomolecular changes that don’t accurately mimic the subtle changes caused by smaller doses delivered over longer periods of time,” explains first author Santosh Paidi, a Johns Hopkins University mechanical engineering graduate research assistant.

“This is only the first step of a larger research endeavor to determine how head and neck cancer tumors respond to radiation,” says Barman. “The ultimate goal is to build a miniature probe that can fit into a laryngoscope. Hopefully in the future, then, when clinicians perform an endoscopy and look at a patient’s cancerous tumor, they’ll be able to determine whether that tumor will even respond to radiation therapy, and that can improve treatment plans.”