Sen. John McCain receiving treatment at Walter Reed Medical Center

Sen. John McCain is receiving treatment at Walter Reed Medical Center, according to his office.

Sen. McCain's office released the statement Wednesday afternoon, saying Sen. McCain is receiving treatment at the center, for normal side effects of his ongoing cancer therapy.

In July, Sen. McCain announced he was diagnosed with Glioblastoma, a highly aggressive form of brain cancer. Last month, the McCain family revealed in People magazine that doctors found a second brain tumor, during treatment.

According to the Associated Press, Sen. McCain has missed votes in the Senate this week, and did not attend a White House ceremony in which President Donald Trump signed the defense bill into law. The sweeping policy bill has been a major achievement of McCain's for years -- especially now, as he is the chairman of the Armed Services Committee. 

In the statement, McCain's office said he is looking forward to returning to work, as soon as possible.

Doctor weighs in on cancer treatment's effect on the body

Dr. Matthew Callister with Banner MD Anderson Cancer Center weighed in on how cancer treatment can affect a person's body.

"Cancer causes fatigue, but also can be hard on the body," said Dr. Callister. "Lack of appetite, weight loss, dehydration, those things are common."

Dr. Callister said oftentimes, the age and health of the person can have an effect on how the body reacts to treatment, as well as what kind of treatments the patient is able to receive.

"We have some main tools for treating cancer. Surgery, drugs and radiation can be done," said Dr. Callister. "We can combine two drugs at the same time. Chemo and radiation, the side effects can be worse short term, but treatment is more effective."

The Associated Press (AP) contributed to this report.