Doctors gave Edie Littlefield Sundby just three months to live. That didn’t mean she got busy planning to die.

To get away from the negative effects of her cancer treatment, she decided to undertake an amazing series of walks on the California Mission Trail from Loreto, Mexico, to Sonoma, California — totaling 1,600 miles.

That was in 2013, but the story of this married mother of three and Oklahoma native began far earlier and is far more layered than it sounds at first. In 2007, doctors diagnosed Sundby with stage 4 gallbladder cancer. The cancer apparently began in her gallbladder but had spread to nine other organs. She was given a less than 1 percent survival rate.

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“I became a walking prayer,” Sundby told LifeZette in an interview. “Every step was a prayer.”

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“Dear Lord, have mercy on me,” Sundby says she prayed along the California trail.

“It took five years, almost one million milligrams of chemo, and radical liver and lung surgeries to subdue my stage 4 cancer. After all of that, my doctors were honest: ‘We will see this cancer again at some point — and then we’ll deal with it as best we can,'” Sundby wrote in an op-ed for Christianity Today.

Her new book, “The Mission Walker,” out this week, shares the details of her life-sustaining journey. Along the way, she felt grateful to be alive.

Sundby, 61 years old in February 2013, found her way to the historic 800-mile trail on the El Camino Real mission from San Diego to Sonoma, California. It took her 55 days to walk the trail; she stopped at 21 Spanish missions along the way. Even more incredibly, she did all of this after most of her right lung had been removed.

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Sometimes she coordinated her movements with her breathing. As she walked along, hour after hour, she breathed, “grace in” and “cancer out.” “A thousand steps became a thousand prayers,” she said.

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Sundby’s physical and spiritual health improved as she trekked along. She connected with God and went through a “spiritual cleanse.” She also processed the emotions that had built up during her fight with cancer, during which she went through 79 rounds of chemotherapy and four major surgeries.

“I was a hostage,” Sundby said. “I was under siege to the cancer.”

Sundby found spiritual renewal in walking.

“It was a bit absurd, since I had never walked more than seven miles in my life, and lung surgery, less than six months before, left me short of breath just walking up stairs,” she wrote in a blog post for The New York Times in 2013.

Franciscan friars and parish priests greeted Sundby along the way. She was accompanied for parts of the journey by a variety of friends and family members.

Two years later, after her first 800-mile journey, her cancer came back — it entered her remaining lung.

“I had this deep yearning to go down to Mexico and finish what I had started,” Sundby said.

So she decided to walk 800 miles on the El Camino Real trail from Loreto, Mexico, across the border to San Diego.

Sundby, who today is just shy of her 66th birthday, has had cancer come back several times since. Her advice for other people: “Don’t delay what you want to do.”

As she writes in her new book about when she first heard her cancer diagnosis: “I had been looking forward to a long life, eventual retirement, travel, grandchildren, and more, and then in a span of an hour, it all seemed to be ripped away.”

Said Sundby today, “That’s what cancer teaches us. Don’t delay what you need to do — you must do [it] now, because we’re all closer to death than we think. We’re all mortal. We never know when God is going to call us home.”

(photo credit, homepage and article images: Edie Littlefield Sundby)