As Rush Limbaugh and Shannen Doherty revealed cancer diagnoses this week, the questions arise: What exactly is stage IV cancer and how is cancer diagnosed?
Limbaugh, the longtime conservative radio host, said Monday he was diagnosed with an “advanced lung cancer.” Limbaugh, who was awarded Tuesday with the Presidential Medal of Freedom during the President Donald Trump’s State of the Union speech, said his diagnosis was confirmed by two medical institutions Jan. 20.
Doherty, the “Beverly Hills, 90210” alum, also announced her cancer diagnosis this week, telling “Good Morning America” on Tuesday that she was diagnosed with stage IV cancer after first being diagnosed with breast cancer in 2015.
Here’s what to know about cancer diagnoses:
What are the stages of cancer?
Cancer staging refers to how doctors classify the extent of a patient’s cancer, including how the cancer has spread in their body and how much cancer there is, the American Cancer Society says.
Doctors use staging to help with treatment and determine a prognosis. But staging alone is not the only factor considered.
According to the National Cancer Institute, the TNM system is most commonly used as it applies to many types of cancer. When a cancer is diagnosed and the TNM system is employed, patients will be given a letter and number that follows, such as T1N0MX or T3N1M0, the institute says.
T generally refers to the original, or primary, tumor and its size or spread. TX means it cannot be measured, T0 means it cannot be found and T followed by a number refers to how large or how much it has spread to nearby tissue. A higher number followed by T means the larger or more widespread the tumor.
N generally refers to whether the cancer has spread to nearby lymph nodes. Similar to T, NX means cancer in nearby lymph nodes cannot be measured, N0 means the cancer has not spread to nearby lymph nodes and N followed by a number refers to the number, location and/or size of lymph nodes with the cancer.
M generally refers to whether the cancer has metastasized, meaning spread to other parts of the body. MX means this cannot be measured, M0 means the cancer has not spread and M1 means it metastasized.
After determining the TNM staging, doctors assign it a more general staging number, often between stages I and IV.
According to the National Cancer Institute, stages I through III mean cancer is present. A larger number indicates the tumor is larger and the cancer has spread more in nearby tissue.
Stage IV cancer indicates the cancer has spread to other, more distant parts of the body, the institute says.
This often happens as the cancer spreads through a patient’s blood stream, said Dr. James Abbruzzese, a medical oncologist at Duke University who specializes in pancreatic cancer.
While Limbaugh said he has “advanced lung cancer,” an advanced cancer does not always mean it is also a stage IV cancer, as cancer can be advanced but not have spread to other parts of the body, according to the American Cancer Society.
Stage 0 indicates “abnormal cells are present but have not spread to nearby tissue,” the National Cancer Institute says. This is also called carcinoma in situ.
Other factors beyond TNM staging can also affect the overall stage, the American Cancer Society says. Grade measures how abnormal cells look under a microscope and how quickly they’re likely to grow and spread. Cell type, tumor location and blood levels of certain substances, called tumor marker levels, also can affect the overall stage, the American Cancer Society says.
Is stage IV cancer always fatal?
While it’s generally easier to treat earlier stages of some cancers with surgery or radiation given that they are more localized, stage IV cancers are treatable, too, said Dr. Lecia Sequist, a medical oncologist at Massachusetts General Hospital Cancer Center who specializes in lung cancer.
“Survival is driven by more than just the staging,” Abbruzzese said. Depending on the type of cancer and how responsive it is to therapy, it’s possible for patients with stage IV cancer to live longer lives, he said.
Still, Sequist said, “The reason why those words, ‘stage IV cancer,’ have such a weight to them is often it does portend a more serious situation.”
For those cancers in cases where the cancer spread to distant parts of the body, breast cancer had a 27.4% five-year survival rate compared to 2.9% five-year survival rate for pancreatic cancer.
Prostate cancer had a 98% five-year survival rate between 2009 and 2015, with a 30.5% survival rate in cases where the cancer spread to distant parts of the body. For lung and bronchus cancer, the five-year survival rate was 19.4% with a 5.2% survival rate in cases where the cancer spread to distant parts of the body.
Stage IV breast cancer isn’t the same as stage IV lung cancer or stage IV pancreatic cancer
While many cancers use the numbered stages, what that stage means for cancer care can vary greatly depending on the type of cancer, Abbruzzese said.
For example, a stage II breast cancer and stage II pancreatic cancer may not have the same prognosis and could have different risks of recurrence after the initial cancer is treated, he said.
That’s because the biology of various cancers differ greatly, said Sequist.
Some cancers are more aggressive in how quickly they spread. For example, breast cancers with more estrogen and progesterone receptors than normal may grow more quickly. According to the National Cancer Institute, testing for this would help determine whether treatments to block estrogen and progesterone are needed.
Additionally, there are different ways doctors stage a patient’s cancer within the TNM system, depending on the type of cancer, the American Cancer Society says.
“In some types of cancer, the T categories describe the size of the main tumor, while in others they describe how deeply the tumor has grown in to the organ it started in, or whether the tumor has grown into nearby structures (regardless of its size),” the American Cancer Society says.
Other cancers, including brain and spinal cord tumors and blood cancers, use different staging systems, according to the National Cancer Institute.
The American Cancer Society says many brain tumors often spread to other parts of the brain but not the lymph nodes or other parts of the body, so they do not use the TNM system.
Leukemias like Adult Acute Lymphoblastic Leukemia or Adult Acute Myeloid Leukemia have no standard staging system. But Chronic Lymphocytic Leukemia does have a staging system based on the number of lymphocytes in the blood, platelets and red blood cells and the size of lymph nodes, liver or spleen, according to the National Cancer Institute.
Follow USA TODAY’s Ryan Miller on Twitter @RyanW_Miller