The New Diagnostics

In cancer, a pathologist is the physician who diagnoses the type of tumor a person has by studying cells and tissues under a microscope. The pathologist also provides information on how the tumor may grow, its stage or grade, and other basic characteristics. But now, because of personalized medicine, pathologists have a new and important role to play: helping to guide oncologists in choosing the most effective personalized treatment.

There are a number of different tests that pathologists can perform to learn more about the genetics of a tumor and the subclass it belongs to. This information helps point the way to the best personalized treatment. Through a fairly new field called proteomics, powerful new tools are being developed to find the genetic features of tumor cells. The “proteome” (a blend of the words “protein” and “genome”) is all the proteins our genes make; proteins do most of the work in cells. The genome is our complete genetic material.

New technologies allow pathologists to extract genetic material from stored tumor samples and to sort out thousands of pieces of genetic material in new tissue samples from a tumor. These techniques enable doctors to identify specific genes. It is a rapidly growing area of medicine that is vital to cancer treatment.

With proteomics, doctors can also identify the proteins that govern how each person will process, or metabolize, drugs. This is another important part of choosing effective treatment. For example, those with a mutated (changed) form of the DPD gene have difficulty metabolizing 5-fluorouracil, a common anti-cancer drug. That’s because the mutated gene does not make the needed DPD protein. As a result, people with a mutated DPD gene experience more side effects from this chemotherapy. This drug is used to treat a number of cancers including breast, stomach, pancreas, and certain types of colorectal and head and neck cancers. If a doctor knows the patient has a mutated DPD gene, he or she can choose another treatment or reduce the dose of 5-fluorouracil. In another example, people who are “fast metabolizers” of anti-nausea drugs can be given a higher dose so the medicine will stay in their system longer and work better.

The more your doctor knows about your genetic makeup, the more effective treatment you can receive.