Norm Coleman outside his Washington, D.C. office in 2015. The former Republican U.S. senator is backing state Sen. Karin Housley in the special election for the seat he once lost to Al Franken. (Special to the Star Tribune/The Minnesota Star Tribune)

The throat and neck cancer that former U.S. Sen. Norm Coleman began battling almost three years ago has spread to his lungs and is at the most advanced stage, Coleman announced Tuesday in a contemplative social media post that touched on family, prayer and New York Yankees great Lou Gehrig.

"The prognosis for metastasized cancer is typically not optimistic," the 68-year-old wrote. "But, the DNA of my cancer has shown great responsiveness to chemo and radiation treatment. My physicians at the Mayo Clinic remain optimistic that the beast can still be contained."

A troubling annual scan at the Rochester clinic led to testing of lung tissue that confirmed a "sobering verdict" that the lesions in his lungs are cancerous, Coleman said.

In October 2015, Coleman had surgery for cancer at Mayo in Rochester after a parched throat signaled that a squamous cell cancer in his right tonsil had spread to the lymph nodes in his neck. He wrote that the cancer was surgically removed along with 39 lymph nodes. He then began a trial program that included smaller doses of chemotherapy and radiation, "based on the belief that the type of cancer I had was much more responsive" to treatment, he wrote.

The lower doses meant improved quality of life, clean scans and relatively minor side effects, he said. Overall, participants in the trial have had relapses at the same percentage as those who have taken more substantial doses. But Coleman is in the 10 percent who experienced recurrence.

He described his soul as shaken but his spirit unbroken, and his belief in prayer strong. Coleman called cancer insidious, relentless and brutal. "Once it is in your body, even if you have wiped away all current traces of it, you live in fear that it will soon emerge from the microscopic shadows," he said.

The former senator began his Facebook announcement by explaining his new hairdo — a buzz cut compliments of his medical team at the Mayo Clinic and his first five-hour paclitaxel and carboplatin chemotherapy session.

While he said he won't know what the journey ahead looks like, he's never felt in better shape and is beyond the moments of "sheer terror" he experienced immediately after his first diagnosis.

He mentioned his wife, Laurie, their two grown children and the two children they lost as infants because of a genetic condition, saying nothing he has done has "compared to the joy of having my children or the sadness that came with losing them."

Coleman talked of his 35 years in public service that started in the Minnesota Attorney General's Office fresh out of the University of Iowa law school and ended with six years as a U.S. senator before he lost to former Sen. Al Franken, a Democrat.

Pat Anderson shared the 2002 Republican ticket with Coleman when she ran for state auditor and he ran for the U.S. Senate. But she first came to admire the charismatic politician while he was the mayor in St. Paul.

"He was the best mayor St. Paul had had in a long time," said Anderson, who served on Eagan's City Council and then as its mayor. "St. Paul was dying. He revived it."

Coleman sets a high bar for public service, said former U.S. Rep. John Kline. "He's worked tirelessly … for his city, state and country," Kline said. "He's a wonderful, wonderful guy."

Kline said he felt better after talking to Coleman on Tuesday. "He's extraordinarily upbeat, laughing," Kline said.

Coleman, a lobbyist with Hogan Lovells in Washington, is still engaged in his work and is playing golf and pickleball, he said.

"It will be what it will be, but we shouldn't be too hasty in writing Norm Coleman off," Kline said.

The New York City native, one-time DFL mayor of St. Paul and Vietnam War protester who converted to the Republican Party said he still returns to Minnesota most weekends and goes to the lake home. He talked about watching the sun and moon, fishing and enduring many more winters before closing with Gehrig's famous parting words at Yankee Stadium when he was forced to retire because of ALS.

"So, I close in saying that I might have been given a bad break, but I've got an awful lot to live for. Thank you," he wrote.

Staff writer M.L. Smith contributed to this report.

Rochelle Olson • 612-673-1747 Twitter: @rochelleolson