Genetic test predicts sensitivity of tumors to radiation therapy

Researchers at a Florida cancer center have developed a genetic test that analyzes the sensitivity of tumors to radiation therapy, with the aim of bringing a form of personalized medicine to the commonly used cancer treatment.

The researchers from Moffitt Cancer Center in Tampa, Fla., developed a radiation sensitivity index (RSI), which predicts how sensitive tumors are to radiation based on expression patterns of different genes. In a study published recently in The International Journal of Radiation Oncology, Biology and Physics, the researchers found that metastatic tumors vary in sensitivity to radiation therapy depending on where they are in the body.

For the study, the researchers used the RSI to determine the radiation sensitivity of 704 metastatic and 1,362 primary colon tumors. Along with finding that the metastatic colon tumors were more resistant to radiation therapy than the primary tumors, the researchers also discovered that the cancer that had metastasized to the lungs had a better response to radiation therapy than the cancer that had metastasized to the liver. This had been predicted by the index.

Dr. Javier Torres-Roca, director of clinical research and associate member of the Department of Radiation Oncology at the Moffitt Cancer Center, said that while radiation therapy is the most commonly used cancer treatment, the idea of personalized medicine has mainly focused on the delivery of chemotherapy, and patients continue to receive a uniform radiation dose.

“Everyone is treated like they have the same tumor, and that is biologically not true,” Torres-Roca told HCB News.

While one possible interpretation of the study is for doctors to consider the site of the metastases in developing dosing protocols, “the more interesting interpretation and direction is that we should be thinking about integrating the RSI into dosing decisions, rather than delivering the same dose,” Torres-Roca said. “It should be delivering the right radiation dose at the right time.”

Researchers at Moffitt are working on technology to customize radiation dose to match the radiosensitivity of the tumor, and Torres-Roca said they expect to get the technology out in the next year or so.

“This is a very important resource for the development of personalized medicine,” Torres-Roca said.

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