Cancer is typically classified by where the cancerous tissues originated—so cells clustering in the lungs are called “lung cancer,” and those in the throat are “throat cancer.” But many kinds of cancer affect more than one kind of tissue, which can make diagnosis and treatment complicated. So what if we thought about cancer not in terms of where it is located but rather by more precise molecular and cellular criteria? That’s what new research from the University of California, San Francisco, is proposing.
A study published today in the journal Cell suggests that 1 in 10 cancer patients could be more accurately diagnosed if cancer were defined by molecular and genetic characteristics. Researchers believe that reclassifying cancer by identifying the type of cell that caused the disease, instead of the tissues where it originated, could ultimately lead to better treatment in the future.
“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,” says co-senior author Dr. Christopher Benz, a professor at the Buck Institute for Research on Aging.
The study analyzed 3,500 tumor samples using genomic technology to analyze their molecular and genetic characteristics. The scientists looked at RNA, DNA and protein samples from the tumors to see how they measured up to each other.
Of the 12 cancer subtypes they discovered, five correlated with traditional tissue-of-origin categorizations. But the rest were previously unidentified subtypes that affected more than one kind of tissue, for which the old classification system wouldn’t apply. For instance, results identified at least three different kinds of bladder cancer. Benz says this might explain why patients with bladder cancer often respond differently despite being treated with the same “systemic therapy for their seemingly identical cancer type.”
The Cancer Genome Atlas (TCGA) project, the National Cancer Institute and the National Human Genome Research Institute collaborated on the project. The TCGA was launched in 2006 in an attempt to amass genomic data for over 20 types of cancer. As the project has advanced, similarities in different cancer types began to surface, which led to the inception of the TCGA’s current “Pan-Cancer” initiative. The data in the Cell study came from the Pan-Cancer initiative.
Once more tumor samples and types are included in the Pan-Cancer project’s next rounds, Benz thinks many more cancer types will be reclassified —he estimates it could be up to 30 to 50 percent. Researchers hope the study will encourage additional trials rooted in genomic reclassification so that state-of-the-art treatment can be developed.
“It will ultimately provide the biologic foundation for that era of personalized cancer treatment that patients and clinicians eagerly await,” Benz says.