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100 miles and one year of living cancer-free

If you think running 100 miles is hard, try doing it on the one-year anniversary of your last chemotherapy treatment.

Jess Daddio

December 2nd, 2023

8 min read


Cassie Cilli had never vomited so much in her life. Even with the support of her rockstar crew, the nighttime hours of the 2021 High Lonesome 100 in Salida, Colorado, had been brutal. Fifty miles in, Cilli’s legs were spent from slogging up and over the course’s high alpine passes. The High Lonesome 100 packs a quad-crushing 23,500 feet of climbing through the Sawatch Range of Colorado’s Rocky Mountains, and Cilli dreaded what was still to come. The scorching late-July temperatures didn’t help. Though the cover of darkness brought a little relief from the scathing sun, the heat had taken its toll. 

Then, there were the pizza rolls. Sustenance is precious during a 100-miler. Cilli knew she needed the fuel, so she choked down the rolls her crew fed her at the Hancock aid station. But just an hour later, her stomach rebelled. She threw up again, and again, and again. Moving slower by the mile, barely on track to beat the aid station time cutoffs, Cilli kept inching toward daylight, one step at a time.

Cilli had been here before. Not the “here” of the High Lonesome, nor the “here” of the 100-miler (though she’d finished two in the five years prior). Cilli had been “here,” the metaphysical darkness, the deep pit of despair where suffering of any kind inevitably dumps you. Cilli was a breast cancer survivor, and exactly one year before she found herself barfing up pizza rolls in the midst of the High Lonesome 100, she’d finished her last infusion of the anticancer drug Herceptin.

In a way, Cilli’s journeys through ultrarunning and breast cancer are linked. Had it not been for the Tarawera 100-miler in Rotorua, New Zealand, it’s possible Cilli never would have discovered the lump in her left breast. It was February 2019, and Cilli, then 32 years old, was living in New Zealand, scraping by on server tips and trail-running adventures. When she toed the line for the Tarawera 100 miler, she was the healthiest she’d ever been, both physically and mentally. Cilli had started trail running just three years beforehand when she was 29, a time in her life she says was marked by toxicity.

“I was struggling mentally and had some substance abuse,” she says. “I was in a slump, but I had a moment where I was like, ‘I’m gonna end up dead one of these days.’ I just wanted to start over with something that could be my own thing and rise above what I was doing.”

Cilli started trail-running in 2016. Only three years later, she had a handful of ultras under her belt, including epic races like the Tarawera 100. Photo Credit: Tarawera 100

Cilli started trail-running in 2016. Only three years later, she had a handful of ultras under her belt, including epic races like the Tarawera 100. Photo Credit: Tarawera 100

So she started trail running. In 2016, she entered the Leadville 100 lottery. To her surprise, she got in. Though Cilli DNF’d , she completed 50 miles of the demanding course, which was farther than the sole road marathon she’d run in her past. Discouraged but not defeated, she kept running. With the help of the Rocky Mountain Runners, a Boulder-based trail-running group, Cilli put in the work. In 2017, her second year of trail running, she finished the Golden Gate Dirty Thirty, the Silver Rush 50, and the Run Rabbit Run.

Trail running empowered Cilli. It was ruthless in its honesty and Cilli respected the blunt accountability her new sport demanded. It forced her to take a hard look at herself, to rise to the occasion, to step into her own strength. Which is why, in 2018, she left Colorado, the only home she had ever known, for the big mountains of New Zealand. 

For Cilli, the 2019 Tarawera 100 was special in more ways than one. She finished the rugged 100 miles in just over 31 hours, shaving nearly four hours off of her previous 100-miler time at the Run Rabbit Run. But it was the finisher’s prize—a locally carved greenstone toki—that meant the most. Greenstone, or pounamu, is renowned by the Māori, New Zealand’s Indigenous people, for its protective qualities. It’s been said that some pounamu choose the individual as much as the individual chooses the stone. 

From the moment Cilli selected her greenstone pendant, she felt it was meant for her. She wore the gem around her neck as a symbol of her strength. It was a reminder she would need. One day she reached for the pounamu resting at her sternum, a mindless fidget she’d developed, only to discover a lump in her left breast. Just four months after her finish at the Tarawera, Cilli was diagnosed with stage two, triple-positive breast cancer.

“It was a shock to the system to say the least,” says Chilli. “You think you can eat all of the kale in the world and escape it, but it just happens, and that’s what happened to me.” 

Cilli continued chugging up mountains, even amid rounds of chemo. “I slept for two days after this effort to recover,” she says. Photo Credit: Cassie Cilli

Cilli continued chugging up mountains, even amid rounds of chemo. “I slept for two days after this effort to recover,” she says. Photo Credit: Cassie Cilli

She returned home to Colorado and began treatment immediately. Chemotherapy sessions every three weeks for four months. A lumpectomy. Lymph node removal. Then, radiation every day for six weeks. Running took a backseat to her healing, but still, Cilli tried to see the light. Day after day, she put one foot in front of the other. Her Rocky Mountain Runners crew set up a GoFundMe site to help cover her medical expenses. When she started losing hair, she rocked a mullet. When she didn’t have the energy to run, she walked. She told bad puns about her “ta-tas,” played with her friend’s dog, watched reruns of Gossip Girl. And, when she finished treatment, she signed up for the High Lonesome 100.

“After closing that chapter, I wanted to feel normal again,” she says. “To celebrate a year of being cancer-free I showed up at the start line for High Lonesome, which I don’t know what’s harder, cancer treatment or running that race a year after.” 

Somehow, Cilli made it through the night of pizza roll-induced vomiting, but the insufferable heat returned. Then, it hailed. Lightning, thunder, and torrential rain pummeled the ridgeline. Cilli and her pacer hunkered down under a fallen log and watched the trail wash past them. With only 10 miles left of the High Lonesome 100, Cilli was ready to call it quits. 

“I didn’t survive cancer to die in the woods because of some stupid race,” Cilli told herself.

Completing the 2021 High Lonesome 100, just one year after completing her breast cancer treatment. Photo Credit: High Lonesome 100

But at the next aid station, her crew was waiting, a beaming beacon of positivity. They fed her food, stripped her wet clothes, dressed her in dry layers. They reminded her of all that she had overcome, of the light that always shines after the rain. Cilli rallied and finished just 20 minutes before the 36-hour cutoff.

“After chemo you want to die, you want to lay down there and not get up—and you have to dig yourself out of that,” she says. “Celebrating by running these hard but fun races brings me back to remembering what I went through, and embracing it and honoring it. It’s my tradition now.”

2 thoughts on "100 miles and one year of living cancer-free"

  1. ron cilli says:

    this lady is such an inspiration for all–toughness and endurance when life is in the down cycle—but ya get your butt up and keep trying—————–shes my daughter and incredibly proud of her accomplishments——-KEEP ON KEEPIN ON—–

  2. Meg says:

    Incredible. Cassi, your dad is right – you are an inspiration!

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