How serious is stage 3 cancer?

Stage 3 cancer is moderate to severe and indicative of widespread disease. Indicators include large tumor size and potential spread of the tumor past the originating organ to adjacent tissues, organs or lymph nodes, according to the National Cancer Institute.

Cancer can be stage 0 (in remission), 1, 2, 3 or 4, states the National Cancer Institute. Stages 1 through 3 all indicate tumor spread to adjacent tissues, with a higher number indicating more severe disease. Stage 4 indicates that the tumor has spread to distant, nonadjacent tissues, such as lung cancer spreading to the bone marrow or the liver. Higher staging at diagnosis indicates a worse prognosis in most cases.