Changes to the way cancers are classified could lead to more accurate diagnoses and perhaps more effective treatments in about one in 10 cancer patients, new research suggests.
Typically, cancers are categorized according to the tissue in which they originated, such as breast, bladder or kidney cancer. But tissues are composed of different types of cells.
Tumour samples analysed
In this study, researchers who analysed more than 3,500 tumor samples of 12 different cancer types concluded that defining tumours by their cellular and molecular features, rather than by the tissues in which they originated, would improve diagnoses in about 10 percent of cancer cases.
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"This 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," study co-senior author Dr. Christopher Benz, professor at the Buck Institute for Research on Aging at the University of California, San Francisco, said in a university news release.
The study, published online in the journal Cell, is part of The Cancer Genome Atlas initiative, which is led by the U.S. National Cancer Institute and U.S. National Human Genome Research Institute.
The researchers report particularly significant findings in bladder and breast cancers. They identified at least three different subtypes of bladder cancer, including one that was nearly identical to a form of non-small cell lung cancer called lung adenocarcinoma, and another most similar to squamous-cell cancers of the head and neck and of the lungs.
The findings may explain why bladder cancer patients "often respond very differently when treated with the same systemic therapy for their seemingly identical cancer type," Benz said.
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The researchers confirmed known differences between two forms of breast cancers called basal-like and luminal. But they also discovered that these differences are significant and that basal-like breast cancers – commonly referred to as triple-negative – are a distinct class of tumour.
"What's amazing is that basal breast cancer is as different from luminal breast cancer as it is from, say, kidney cancer," study co-lead author Denise Wolf, a research scientist based in UCSF's Department of Laboratory Medicine, said in the news release.
Basal-like cancers are highly aggressive and more common among black and younger women.
"Even though these basal-like cancers arise in the breast, on the molecular level they have more in common with ovarian cancers and cancers of squamous-cell origin than with other subtypes of breast cancer," explained study co-lead author Christina Yau, a staff scientist at the Buck Institute and assistant professor of surgery at UCSF.
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"This is the first time ever you've been able to point to important molecular features shared by basal breast cancer, and by squamous head-and-neck cancer and lung cancer," Wolf said.
"And the same is true of immune activation – we found that different cancer types have very similar immune signatures, a factor that may be relevant clinically with the rise of new immune therapies," she added.
Further research could reveal that as many as 30 to 50 percent of cancers need to be reclassified, according to Benz.
"Although follow-up studies are needed to validate and refine this newly proposed cancer classification system, it will ultimately provide the biologic foundation for that era of personalised cancer treatment that patients and clinicians eagerly await," Benz believes.
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