New York 19th March 2020 : A study by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, offers new insight into genetic alterations associated with osteosarcoma, the most common cancerous bone tumour of children and adolescents. The researchers found that more people with osteosarcoma carry harmful, or likely harmful, variants in known cancer-susceptibility genes than people without osteosarcoma. This finding has implications for genetic testing of children with osteosarcoma, as well as their families. The study was published March 19, 2020, in JAMA Oncology. “With this study, we wanted to find out how many people with osteosarcoma may have been at high risk for it because of their genetics,” said Lisa Mirabello, Ph.D., of NCI’s Division of Cancer Epidemiology and Genetics (DCEG), who led the research. “We not only learned that at least a quarter of the people in the study with osteosarcoma had a variant in a gene known to predispose someone to cancer, we also uncovered variants that had never before been associated with this cancer.” In the study, the researchers looked for harmful (or likely harmful) variants in 238 known cancer-susceptibility genes in DNA samples from 1,244 people with osteosarcoma and compared the frequency of such variants with that in people in a cancer-free control group. They identified a harmful or likely harmful variant in a known cancer-susceptibility gene in 28% of the people with osteosarcoma. By contrast, only 12% of people in the cancer-free control group had such a variant. When the authors looked at a subset of 166 genes that are known to be inherited in an autosomal dominant fashion—that is, where inheriting one alteration from one parent is sufficient to increase cancer risk—they saw harmful or likely harmful variants in about 18% of the patients but only 5% of controls. And another 25% of the patients had a rare variant of uncertain significance that was predicted to be harmful. Patients who had harmful variants were younger at age of osteosarcoma diagnosis, on average, than patients who did not (15.3 years versus 16.9 years). In addition, the youngest children…