A research network in the US proposes that cancer should be classified according to genetic and molecular features rather than by the type of tissue in which the tumor arises. While more work is needed to confirm and build on findings that look set to rewrite oncology textbooks, the scientists say such a system would be better for patients because it would help tailor treatment to their individual needs. Share on Pinterest Researchers found that different types of cancerous tumors were molecularly and genetically similar, prompting them to challenge the existing system of classifying cancers. Writing about their findings in the journal Cell, researchers from The Cancer Genome Atlas (TCGA) describe how they analyzed more than 3,500 tumors on multiple genomic technology platforms. There have already been studies that suggest cancer should be defined by features at the genetic and molecular level. For example, Medical News Today recently reported another TCGA study that found four distinct molecular subtypes of stomach cancer. But in this latest study – the largest genomic study of cancer – the researchers found even across tissue types (for instance, breast, bladder and kidney), what we currently regard as different cancers have tumors that are more similar at the molecular and genetic level than at the tissue level.

‘Disruptive’ study challenges existing system of classifying cancers In explaining the impact of the findings, co-corresponding author Chris Benz, a professor at the Buck Institute for Research on Aging in Novato, CA, points out most of our tissues comprise many different types of epithelial and non-epithelial cells (epithelial cells being those that line cavities in the body and cover flat surfaces, while non-epithelial cells form other tissue types such as connective, muscle and nervous tissue), and: “This disruptive genomic study not only challenges our existing system of classifying cancers based on tissue type, but also provides a massive new data resource for further exploration as well as a comprehensive list of the molecular features distinguishing each of the newly described cancer classes.” He cites the example of bladder cancer, which they propose should be reclassified into several different types, each with distinct and different outcomes, to explain why patients can expect quite different results when treated with the same systemic therapy. For the study, the scientists compared the DNA, RNA and proteins of 3,527 specimens of 12 different tumor types by analyzing them with six different “platform technologies.” The results showed tumors were more likely to be molecularly and genetically similar based on their cell type of origin as opposed to their tissue type of origin.