Senator John McCain Stops Medical Treatment for Brain Cancer

John McCain is making a difficult decision in his year-long battle with brain cancer.

The longtime U.S. Senator from Arizona has decided to stop medical treatment for the disease ... according to the Republican's family.

As we reported ... McCain was diagnosed with brain cancer -- known as glioblastoma -- last July. He'd been receiving treatment from his home near Sedona, Arizona since December.

The 81-year-old is a 6-term Senator and was the 2008 Republican presidential nominee.

McCain's family said age is a factor in John's decision to stop getting treatment ... and he's already surpassed expectations for his survival.

A statement from McCain's family says, "John has surpassed expectations for his survival. But the progress of disease and the inexorable advance of age render their verdict. With his usual strength of will, he has now chosen to discontinue medical treatment."

The statement continues, "Our family is immensely grateful for the support and kindness of all his caregivers over the last year, and for the continuing outpouring of concern and affection from John's many friends and associates, and the many thousands of people who are keeping him in their prayers."

McCain has served in the Senate since 1986. He was elected to the U.S. House of Representatives from Arizona in '82.

Before his political career, McCain entered the Naval Academy in 1954 and served in the Navy until '81.