Tom Brokaw's Cancer, Explained

NBC News' Tom Brokaw was diagnosed with multiple myeloma last year, NBC News reported.

Brokaw, who is 74, is a special correspondent at the network. He was diagnosed with the cancer, which affects the plasma cells in the bone marrow, last August at the Mayo Clinic.

"With the exceptional support of my family, medical team and friends, I am very optimistic about the future and look forward to continuing my life, my work and adventures still to come," he said in a statement posted on the NBC News website.

Even though there is no cure for multiple myeloma, the condition is considered treatable, USA Today reported. Survival time has increased significantly: For instance, 20 years ago, people with the cancer only survived two or three years after being diagnosed. Now, they survive five to seven years after being diagnosed, and sometimes even more than a decade.

According to the American Cancer Society, there are expected to be 24,050 new cases and 11,090 deaths from multiple myeloma in the U.S. this year. A person's lifetime risk of developing the condition is one in 149.

Multiple myeloma occurs when abnormal plasma cells in the bone marrow multiply, eventually collecting in the bone marrow and bone. Since plasma cells are responsible for making proteins called antibodies, which are the body's way of fighting infection, that means an increase in the blood levels of abnormal proteins, according to the Mayo Clinic.

As a comparison: In healthy people, plasma cells make up 5 percent of the cells in bone marrow. But in people with multiple myeloma, plasma cells could make up more than 10 percent of the cells in bone marrow, the Mayo Clinic explained. When there are too many plasma cells, it eventually affects the body's immune system.

While the condition may not cause symptoms in its early stages, it can lead to kidney failure, bone damage, fatigue due to anemia, and high blood calcium levels (which manifests as nausea, confusion, constipation and excessive thirst).

If there are not any symptoms from multiple myeloma, doctors may decide treatment is not yet needed, the National Institutes of Health pointed out. However, if symptomatic, the condition may require chemotherapy, radiation therapy, targeted therapy or stem cell transplantation.