Genomics Model Has Potential To Personalize Radiotherapy
January 9, 2017
Genomic-adjusted radiation dose (GARD) is a new genomic model that can predict radiotherapy's therapeutic effect on specific tumors. GARD can help guide the dose of radiation used to match an individual tumor's sensitivity to radiation.
Researchers at Moffitt Cancer Center and Research Institute conducted the study, published online in Lancet Oncology on December 16, 2016. They used a previously developed gene-expression based radiosensitivity index (RSI) that can predict a tumor's sensitivity to radiotherapy based on the expression of 10 specific genes.
The RSI accurately predicts clinical outcomes for breast, head and neck, glioblastoma, pancreas, and metastatic colorectal cancer patients. The RSI was used to develop GARD.
In this study, the researchers used 8,271 tumor samples from patients enrolled in the Total Cancer Care (TCC) cohort and assessed the range of GARD values within and between tumor types. The GARD values ranged from 1.66 to 172.4 across the TCC cohort.
The study authors found that "…a higher radiotherapy dose does not always result in a higher radiotherapeutic effect across a population."1 They also determined that cancers, such as cervical and head and neck, which are usually treated with high doses of radiotherapy, had the highest median GARD values.
Sarcomas and gliomas, which are less responsive to radiation therapy, had the lowest median GARD values.
In a statement, Dr. Louis B. Harrison, chair of Moffitt's Radiation Oncology Department, said, "The GARD model provides the first opportunity to genomically inform radiation dose and is a safe and feasible approach to precision radiation oncology."2
Tailoring treatment to patients' specific biology has led to improved outcomes for some patients. Until now, however, precision medicine for cancer patients has generally focused on drugs. This study suggests radiation therapy dose can be personalized using tumor genomics.
Up to two-thirds of cancer patients in the United States receive radiotherapy.