With about a mile remaining in her first Boston Marathon, Elinor Scott hit a roadblock. As she stood in the street among thousands of other runners, wondering why Boston police had barricaded her final push, she received a text message from her daughter: There had been two deadly explosions at the finish line.

That horrific act, which killed three people and injured more than 260 last April, prevented the St. Louis Park resident from realizing a long-held goal of completing one of the world’s great marathons. Like so many others who were stopped that day, she has longed to finish what she had started. She qualified again for Boston last fall, despite battling myasthenia gravis, a neuromuscular disorder that causes weakness and breathing difficulties. But as Scott continued to train for her goal, another roadblock arose in January: Stage 4 pancreatic cancer.

Surgery and chemotherapy this spring have left her body frail. Determined as ever, Scott still plans to pick up where she left off, returning to Boston on April 21 for a specially arranged final-mile walk to the finish line on Boylston Street.

It’s not the scenario the self-described endurance junkie had in mind, but she has kept faith that she can cross the line in the way she envisioned. “I’m hoping I’ll be able to at least run the last little bit,’’ said Scott, 51, who on April 2 began a second round of more aggressive chemotherapy. “Running across the finish line would be my goal.’’

Unlike other runners who find bliss in solitude, Scott’s love for the sport blossomed when she joined the running club at Life Time Fitness in St. Louis Park. Those friends, and her family, are accompanying her on this arduous journey. While she credits them with keeping her spirit afloat, they say she has done the same for them.

“It’s unbelievable, the courage and power she has,’’ said Sharon Stubler, a fellow member of the Life Time club who has competed in the U.S. Olympic marathon trials. “The odds may not look that good, but if there’s a miracle out there, she’ll find it. She’s the kind of person who will not accept defeat.’’

This year’s 118th running of the Boston Marathon will be a celebration of fortitude and perseverance. In the wake of the bombing, a deeply wounded city gathered itself up and proclaimed itself “Boston Strong.’’

A similar theme has run through Scott’s life since that day last April. She had wanted to tackle the Boston Marathon since she took up the sport in 2009 and got her chance to go last year. By that time, the symptoms of myasthenia gravis already had made running a challenge.

She was slowing but was still on track to finish the race when the runners were stopped. After waiting in the chill and confusion for hours, when Scott finally was able to reunite with daughter Martha Sutter and their friends, she was so ill she could barely stand.

Her health continued to deteriorate through the summer. Her boyfriend and running partner, Ken Rosen, persuaded her to pursue the qualifying time for Boston so she could take another shot at finishing this year. She made it at the Lake Wobegon Trail Marathon, but she worried whether she would be strong enough to actually run in Boston.

“I was very disappointed when I realized how hard it was getting to run,’’ said Scott, who holds a personal-best time in the marathon of three hours, 55 minutes, eight seconds. “The goals kept going from ‘I just have to run faster’ to ‘Just let me run the Boston Marathon once’ to ‘If only I could just keep running.’ It was slipping quickly.’’

Scott tried to keep training. But at the WhistleStop Marathon in Wisconsin in October, she lost the ability to swallow water at mile 18. She could barely breathe, and her legs weren’t functioning properly, but she got across the finish line.

On Jan. 5, Scott ran a mile indoors and had to stop twice to rest. The next day, she was hospitalized. Doctors found blood clots in her legs and lungs, lesions on her liver and a tumor on her pancreas. After her current round of chemotherapy, Scott is planning to participate in trials for a new drug, Minnelide, being developed at the University of Minnesota.

“She wants to beat this,’’ said Rosen, whom Scott met in the running club. “It’s no different than running. Elinor sets goals and does what it takes to achieve them, no matter how hard it is.’’

Rosen said Scott is naturally optimistic, and is surrounded by positive thinkers — including the members of her running club. Many have visited and brought food, and coach Rick Trueman — whose father is a pancreatic cancer survivor — told her about the drug trial. But the best gift came from club member Greg Rosenberg.

At a seminar for coaches and race directors, Rosenberg approached David McGillivray, director of the Boston Marathon. He told McGillivray about Scott, and McGillivray contacted her to get the full story. According to Scott, after clearing it with the marathon’s board of directors and Boston police, he told her two weeks ago that she could walk the final mile.

Her doctors have approved her plan, Scott said, and her mother, Donna Scott, proclaimed it “good medicine.’’ Rosen will be running in the Boston Marathon, and Scott’s mother, her sister Jodi and Martha, 15, also will accompany her.

“Boston was always her dream,’’ said Martha, who was with her friends at the finish line last year just 20 minutes before the bombs went off. “To be able to reach her dream, no matter how hard the battles get, I’m excited to see her do that.’’

Scott has been able to take walks since her diagnosis, though she remains so weak that she can only sit up for a limited amount of time. Not being able to run has left a void in her life. “In my past two marathon trainings, I peaked at 71 or 72 miles a week,’’ she said. “To go from that activity level to being so weak that sitting up is a major activity, that’s quite a change. But I try to focus on the positive things.’’

That includes her big day on April 21, when one mile will feel as exhilarating as 26.2.

“Finishing what she started is very important to her,’’ Rosen said. “It’s an awesome finish at Boston, with all the people cheering. She didn’t get to hear that last year. She wants to cover that hallowed ground.’’