Genetic Test Finds Radiation Sensitivity Differs Between Primary Tumor and Metastatic Sites

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Genetic testing of tumors is driving personalized medicine in medical oncology. A recent study that used a molecular assay to assess the radiation sensitivity of primary tumors and metastases suggests potential for genetic testing in guiding radiation therapy as well.

The study, published July 15, 2015, in the International Journal of Radiation Oncology, Biology, Physics (doi:10.1016/j.ijrobp.2015.01.036), used a previously developed 10-gene assay to calculate a radiation sensitivity index (RSI).....

“Right now, we know clinically that patients have different responses to radiation, but the way we treat them doesn’t acknowledge that,” said study coauthor Javier F. Torres-Roca, M.D., a radiation oncologist at the Moffitt Cancer Center and Research Institute in Tampa, Fla. “Our focus is integrating genomic measures into radiation oncology, not only to understand the mechanisms of the problem but to find ways to treat patients more effectively.”.....

 In the new study, Torres-Roca and colleagues first calculated the RSI for 704 metastatic and 1,362 primary colon cancer lesions. Sixty percent of metastatic tumors were in the RSI radiation-resistant peak, compared with 54% of primary tumors, indicating the metastases might not respond as well to radiation therapy as the primary tumors. They also found statistically significant differences across metastatic sites, with metastases in the ovary and abdomen having the highest RSI scores (0.48 and 0.47, respectively), followed by liver, brain, lung, and lymph nodes (0.43, 0.42, 0.32 and 0.31 respectively)......