Understanding Cancer Language: Tumor Terms Patients Should Know

As cancer care advances with more sophisticated treatment options, it’s helpful to understand what your doctor means when using such terms as tumor biomarker, tumor sequencing, and tumor board.

But first, let’s start with a definition of tumor. A tumor is an abnormal growth of cells in the body that can be cancerous or noncancerous. Most tumors have undergone genetic changes (mutations). These mutations can alter the DNA sequence in the tumor cells and lead to uncontrolled cell growth, which contributes to the development and progression of cancer.

According to William K. Oh, MD, a Yale Medicine medical oncologist and director of precision medicine at Yale Cancer Center and Smilow Cancer Hospital, obtaining tumor biomarkers and conducting tumor sequencing are key steps for cancer diagnosis and treatment. And a tumor board, which is essentially a meeting of physicians to discuss cancer patient cases across various specialties, is important for determining the best treatment plans for complicated cases.

“For cancer, and for all diseases, the more we understand about the biology of what makes that cancer tick or that disease happen, the more we can individualize the best treatment for them to obtain the best outcome,” Dr. Oh explains. “This also allows us to spare people from the treatments that might not work for them, like chemotherapy, for example.”

Tumor biomarkers are substances that can be found in the blood, urine, tissues, or other body fluids that indicate the presence of cancer. They may be produced directly by the tumor or by the body in response to the tumor. These biomarkers can include proteins, DNA, RNA, and other molecules.

Sometimes, the biomarkers are directly related to genetic mutations. Knowing this is helpful to doctors because certain mutations are associated with certain cancers. Identifying a patient’s specific mutation can provide information on how to personalize cancer treatment to make it more effective against that tumor.

For example, the EGFR (epidermal growth factor receptor) mutation is a tumor biomarker that is significantly associated with non-small cell lung cancer.

“Yale researchers were a part of the discovery of EGFR mutations in lung cancer 20 years ago, and it has revolutionized treatment for patients,” says Sanja Dacic, MD, PhD, a Yale Medicine pathologist.

EGFR mutations are called “predictive biomarkers” because their presence indicates whether a patient’s cancer is likely to respond to treatment with EGFR inhibitors, a class of drugs that target the altered EGFR protein to slow or stop cancer growth.

Additionally, biomarkers are useful for showing how well treatments are working for patients, Dr. Dacic notes. “We can study a blood sample, for example, and see the values of the biomarker, which can indicate the risk for the disease recurring,” she says. “Basically, we are examining tumors on a molecular level. The patient may be feeling fine and we see no imaging evidence of the disease, but if these biomarkers are circulating in the blood at certain levels, we have more information that the cancer may come back.”

Tumor sequencing is a technique used to help doctors identify tumor biomarkers and genetic mutations. To perform tumor sequencing, a sample of tumor tissue is collected, often when a surgeon removes a tumor. A tissue specimen is sent to a lab, where the DNA and RNA are isolated and run through a sequencing machine.

By looking at the DNA, doctors can identify the genetic blueprint and potential mutations driving the tumor; studying the RNA offers insight into how these genetic changes affect gene expression and cellular behavior.

Tumor sequencing can also be done via a liquid biopsy, which usually involves drawing blood from a vein in the arm. In the lab, pathologists look for cancer-related biomarkers such as tumor cells circulating in the bloodstream. Less commonly, liquid biopsies are done with other bodily fluids including urine, saliva, and cerebrospinal fluid.

By using tumor sequencing to pinpoint specific mutations, doctors can more precisely diagnose a patient’s cancer and identify treatments that may work best on those mutations.

“Once we can see the damage caused by certain mutations, we can use drugs that have been specifically crafted to help repair that mutation,” Dr. Oh explains. “The most famous example of this is the BRCA genes, which if mutated, can lead to early breast cancer.”

If a woman has a BRCA1 mutation, her risk of breast cancer is about 60% to 75%; having a BRCA2 mutation is associated with 50% to 75% risk.

“We now have drugs that specifically work for people who carry the BRCA mutations and develop cancer. And they work through mechanisms that are only effective in those patients,” Dr. Oh says.

These types of drugs fall into a category called targeted therapy, which includes medications designed to attack cancer cells by exploiting unique weaknesses found in certain cancer mutations, thereby minimizing harm to healthy cells.

For example, radioligand therapies use a radioactive substance that attaches to molecules that bind to cancer cells and destroy them, while sparing most healthy cells around them. Antibody-drug conjugates (ADCs) combine an antibody with a powerful drug. The antibody seeks out the cancer cells and delivers the drugs directly to them, killing them, and often resulting in fewer patient side effects than traditional treatments, including chemotherapy.

Targeted therapy, along with immunotherapy (which uses medication to harness and enhance the body’s immune system to recognize and destroy cancer cells), are both considered precision medicine.

A tumor board is a meeting of cancer specialists who come together specifically to discuss a patient's cancer case and, collaboratively, determine the best treatment plan. Tumor boards often include several different types of specialists, including medical oncologists, surgeons, pathologists, and radiologists.

The specialists gather all relevant information—medical history, imaging, biopsy results, and molecular genetic testing results—to review treatment options, risks, and determine if any additional testing is needed.

Typically, tumor boards focus on cases that are complicated and require special considerations on next steps. At Yale, which the National Cancer Institute designated as a comprehensive cancer center, specific tumor boards—including those for breast, gastroenterology, and genitourinary—meet weekly.

“Put simply, these are doctors who are experts in a specific patient's care. We get together once a week to talk about complicated patient cases. We have tumor boards for all the different disease types,” Dr. Oh explains. “Also, at Yale, for many years we have had an additional one called the Precision Medicine Tumor Board, where we discuss the molecular findings on specific patient samples. Sometimes, these findings may make someone a candidate for a specific treatment or clinical trial.”

Yale Cancer Center, Dr. Oh adds, has a robust Phase 1 clinical trial program, through which new treatments are tested.

“We want to get these novel treatments to patients, and often the only way to do this is to find the mutation that exists in these specific tumors,” he says. “And unless a patient’s tumor is sequenced and presented at a tumor board, we wouldn’t have this information to work with.”

Another benefit of a tumor board, Dr. Dacic says, is that the experts from multiple disciplines meet in person or virtually. “We talk about important information that sometimes cannot be fully expressed by someone reading or viewing a report,” she says. “It’s a collegial atmosphere and we get to discuss everything at once and make decisions, together, that are best for the patient.”