Isabella de la Houssaye, a lawyer and prolific endurance athlete who continued to go on daunting adventures around the world with her five children after being diagnosed with Stage 4 non-small-cell lung cancer, died on Saturday in Hermosa Beach, Calif. She was 59.
Her son Cason Crane said she died of the disease at the house she had rented while continuing her treatments.
Mountaineering, marathoning and triathloning with her daughter and four sons were activities she undertook “in an effort to both teach them skills such as patience, focus, perseverance as well as an appreciation of nature,” Ms. de la Houssaye (pronounced de-la-hoo-SAY) said in an interview in 2022 on the NeoGenomics Laboratories website.
Ms. de la Houssaye began her endurance athletic feats, on her own and with her family, in the 1990s and continued for decades. She climbed Kilimanjaro, the highest mountain in Africa, with her children on separate ascents; finished more than 20 Ironman Triathlons; competed in many ultramarathons; ran in more than 70 marathons; and bicycled across Tasmania.
She and her husband, David W. Crane, started to encourage their children to participate in endurance activities when they were as young as 10 — “a radical form of parenting,” as Cason called it in a phone interview. They first climbed Kilimanjaro with Cason, her oldest child, when he was 15. They decided to scale it as an afterthought, one day after they ran in the Kilimanjaro Marathon.
“It was offered as an option after the marathon,” she said on the “Long Run” podcast in 2020. “I don’t know if either of us knew exactly what we were getting into.”
The ascent was Ms. de la Houssaye’s first of any extremely high-altitude mountain, and it inspired Cason to climb the highest summits on the six other continents by the time he was 20. He is believed to be the first openly L.G.B.T.Q. person to scale them all.
Her athletic activities stopped when she was diagnosed with lung cancer in January 2018 — but only temporarily. The cancer had already spread to her pelvis, brain, spine, sacrum and adrenal gland. But two drugs targeted for non-small-cell lung cancer made her feel better quickly, and she finished a marathon that April using walking poles. In June, she completed a marathon in Anchorage, and this time she didn’t need the poles.
Told that she might live for only six more months, she went on what might have been her final adventures with four of her five children in 2018 and early 2019. With her son Oliver, she hiked more than 500 miles of the Camino de Santiago, a medieval pilgrimage route in Spain. With Cason and her husband, she ran a marathon in Alaska.
With her husband, a lawyer and investment banker who is now the under secretary of energy for infrastructure; her daughter, Bella Crane; and her sons David and Cason, she finished a 100-kilometer ultramarathon in Kazakhstan. A week later, with David, she competed in a full Ironman triathlon in Gurye, South Korea.
In January 2019, when she and Bella started their ascent of Aconcagua in Argentina, the tallest summit in the Americas, she weighed less than 100 pounds. Chemotherapy had made her bones brittle, her breathing capacity had diminished, and she had life-threatening tumors in her brain. During the climb to the 22,840-foot summit, she and Bella faced brutal winds and subzero temperatures.
When they reached base camp, at 14,000 feet, Ms. de la Houssaye declared that Aconcagua would be her last mountain.
“I don’t think I can do this anymore,” she told Rebecca Byerly, a reporter who followed her and her daughter on the climb for The New York Times. “I’m going to take each day at a time but have no illusion that I will get to the top.”
One freezing night, the altitude made Ms. de la Houssaye sick. She vomited several times in her tent and spilled a bottle of urine.
“Bella cleaned it up and between otherwise silent bites of eggs and pancakes at breakfast, she said, ‘I forgive you, mother,’” Ms. Byerly wrote.
“Ms. de la Houssaye looked at her daughter, and her gaunt face lightened with laughter.
“‘This sure was a way to bond,’ she said.”
When they left the next camp, at 19,600 feet, Ms. Byerly wrote: “Isabella had a determined look in her eyes and kept a steady pace. When Bella broke down with fatigue 500 meters from the top, it was Isabella who convinced her daughter that she could make the summit, just as she always had.”
At the top of Aconcagua, mother and daughter embraced, and Ms. de la Houssaye wiped tears from her eyes.
Isabella Livaudais de la Houssaye was born on Feb. 2, 1964, in New Orleans and raised in Crowley, in southwest Louisiana. Her father, Benton Cason de la Houssaye Jr., was a physician. Her mother, Isabella (Livaudais) de la Houssaye, served at different times as the mayor of Crowley and a city councilwoman.
Ms. de la Houssaye majored in politics at Princeton University and received a bachelor’s degree in 1986. After graduating from Columbia Law School in 1990, she joined the law firm White & Case, where she specialized in international law. She moved to Lehman Brothers in 1997 and worked on the firm’s administrative side until leaving in 2005 to focus on raising her children.
In 2008 she became an owner of Material Culture, an art and antiques retail store and auction house in Philadelphia. She lived in Lawrenceville, N.J.
Ms. de la Houssaye, who had always been an athlete, began endurance running with a 100-kilometer race she worked during part of her time at White & Case, and added to her credentials for most of the rest of her life.
After climbing Aconcagua in 2019, she competed in many events, including the Ironman Arizona with her youngest child, Christopher. Three years later she finished the Ironman Cozumel with all five of her children and eight members of her extended family.
In 2020, she bicycled across America with her husband, from San Diego to St. Augustine, Fla. (with a stop in Austin, Texas, for chemotherapy), to raise awareness for lung cancer. In 2023, she walked in marathons on Jan. 31 in Antarctica and, two days later, in Punta Arenas, Chile, with Cason and Oliver.
“Recovery wasn’t in her vocabulary,” Cason Crane said, referring to his mother’s insistence that they do the two exhausting events so closely together. He added, “You looked at this 5-foot-2, 85-pound frame, and you’re thinking that the only way to understand this is the incredible power of the human mind.”
Ms. de la Houssaye is survived by her children; her husband; her mother; her sisters, Elise de la Houssaye Frantzen and Nadia de la Houssaye; and her brother, Benton Cason de la Houssaye III.
She was participating in an experimental drug program in Los Angeles in her final days but nevertheless wanted to compete on Nov. 12 in the Athens Marathon by having Cason push her in her wheelchair.
At Thanksgiving, he recalled, she said to him, “You have to email the Athens Marathon people and tell them I’m still doing it.”
“I didn’t have the heart,” he said, “to say it had already happened.”
