Jennings, ABC's chief anchorman since 1983, planned to be at his desk Tuesday — a day after getting his diagnosis.
A former smoker who quit several years ago, the 66-year-old anchor was too ill to work Saturday during the network's special report on Pope John Paul II's death. He hasn't been feeling well the past few months, and didn't travel under doctor's orders after December's tsunami because of what was described then as an upper respiratory infection. He did go to Iraq in January for the elections.
Lung cancer is the leading cancer killer in the United States, and roughly four out of five people diagnosed with the disease die within five years, said Dr. Cliff Connery, chief of thoracic surgery at St. Luke's-Roosevelt Hospital in Manhattan.
"Overall, lung cancer is the number one mortality for cancer-related deaths in this country, even combining breast, colon and prostate together doesn't add up to lung cancer," Dr. Robert Ashton with St Luke's Roosevelt Medical Center tells CBS News Correspondent Elizabeth Kaledin.
Despite the high mortality rate associated with lung cancer, Kaledin reports, the key to fighting it is catching it as early as possible. If it is found early, the cure rate jumps to 50 percent.