Information that is hidden in imaging tests has the potential to help physicians choose the right radiation therapy dose to kill tumors, according to a study presented at the annual American Association of Physicists in Medicine.

It's currently the largest study that uses radiomics — extracting statistical information from images — to assist in determining the likelihood of cancer progression or its response to treatment based on PET scans of patients with non-small-cell lung cancer and head and neck cancer.

"This is different from what has been done in the past," Joseph Deasy, senior author of the study and chair of the department of medical physics at Memorial Sloan-Kettering Cancer Center, said in a teleconference. "Diagnostic imaging was typically only used to identify the presence of the cancer or to outline the extent of the disease to define the field that gets the high dose of radiation."
For the study, the researchers conducted PET scans on 163 non-small-cell lung cancer patients and 174 head and neck cancer patients before and after treatment. From each tumor, they got information about the intensity value of the PET image, the roughness of the image, the shape of the tumor, etc.

The brightest area on a PET image shows a higher intensity, meaning that the tumor is consuming more energy from the injected radioactive glucose substitute tracer.

The researchers were able to use the before and after scans to determine the outcome of the patients, including whether the tumor minimized and how long they survived. It gives them the opportunity to develop models that can help them dictate therapy in the future.

One of the things they uncovered is that lung tumors that have a higher uptake of the tracer need a higher dose of radiation than is usually prescribed.

"It can help us to keep from over-treating cancers and potentially causing normal tissue toxicity, and it can help us to not under-treat cancers that may need a fairly high dose of radiation to have a good probability of disease control," said Deasy.

Deasy said that the next step is for him and the other researchers to talk to their clinical colleagues about how they want to try to test it a clinical prospective way. To date, they have already had discussions with their radiation oncology physician colleagues.

However, they haven't made a final decision yet. "It's new and it does imply that we should take steps forward but we haven't actually implemented it in the clinic yet," said Deasy.

They're also working with groups at other leading institutes to investigate using other modalities such as CT, volumetric X-ray and MR to determine radiotherapy dose distribution levels. Deasy said that they will be presenting that information at this year's RSNA meeting.

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