Representative John Lewis of Georgia announced Sunday that he will be undergoing treatment for Stage IV pancreatic cancer. The 79-year-old Democratic congressman said he has "never faced a fight quite like the one I have now."

"While I am clear-eyed about the prognosis, doctors have told me that recent medical advances have made this type of cancer treatable in many cases, that treatment options are no longer as debilitating as they once were, and that I have a fighting chance," Lewis said in a statement. "So I have decided to do what I know to do and do what I have always done: I am going to fight it and keep fighting for the Beloved Community. We still have many bridges to cross."

Lewis said he will return to Washington D.C. soon to begin his treatment. While he plans to continue working, he noted, "I may miss a few votes during this period, but with God's grace I will be back on the front lines soon."

Lewis, a civil rights icon, has been the representative for Georgia's Fifth Congressional District since 1987.

"We are all praying for you following this diagnosis," House Speaker Nancy Pelosi posted on Twitter. "John, know that generations of Americans have you in their thoughts & prayers as you face this fight. We are all praying that you are comfortable. We know that you will be well."

Former President Obama also tweeted a message of encouragement. 

"If there's one thing I love about @RepJohnLewis, it's his incomparable will to fight. I know he's got a lot more of that left in him. Praying for you, my friend," Mr. Obama wrote.

According to the latest data from the American Cancer Society, the survival rate over five years for all forms pancreatic cancer at 9%.

Pancreatic cancer is the 10th most commonly diagnosed cancer in men in the United States, and the ninth most common in women. It accounts for about 3% of all cancers but about 7% of all cancer death. It is one of the deadliest forms cancer because there are no screening tests that catch it in its early stages. 

As with other cancers, pancreatic cancer is categorized by stages which describe how far the cancer has spread and how much of the body has been affected. Stage IV is the most severe, meaning the cancer has spread to other parts of the body such as the liver, lungs or bones.