After Mom Dies from Breast Cancer, Sisters Diagnosed With Bone Cancer Vow to ‘Fight Together’. Now, the Youngest Has Died

A young Canadian woman has passed away from a rare and aggressive form of bone cancer — the same disease her older sister is still battling.

Katelyn and Cassandra Harding lost their mother to breast cancer in 2014. Years later, tragedy struck again.

In July 2022, Cassandra was diagnosed with osteosarcoma, a rare type of bone cancer that primarily affects the upper arm or areas around the knee. According to Johns Hopkins Medicine, fewer than 1,000 cases are diagnosed annually in the U.S. The disease can spread rapidly, invading tendons, tissues, and even internal organs.

By the time Cassandra’s cancer was detected, it had already spread from her knee to her femur and tibia. Doctors determined that surgical removal was the only viable option. As a result, she underwent a major operation that replaced her knee, femur, and tibia with prosthetic metal implants. Her treatment also included an intensive 40-week chemotherapy regimen, which concluded in May 2023.

Just one month later, in June 2023, Cassandra’s younger sister, Katelyn, was also diagnosed with osteosarcoma. A GoFundMe campaign created to support the sisters shared that Katelyn’s cancer had already reached her pelvis, tailbone, and spine by the time it was discovered.

The sisters chronicled their parallel battles with cancer through their joint Instagram account, HardingSisters45, offering followers a glimpse into their courage and resilience.

In March 2024, Cassandra revealed another blow — she had developed metastatic sarcoma lung cancer, meaning the cancer had spread to her lungs. Meanwhile, an update on Katelyn’s condition noted she was receiving radiation for a tumor measuring eight inches in her pelvis.

The two sisters remained incredibly close throughout their health crises, often sharing emotional updates and messages of unity. One especially poignant post showed them lying in a hospital bed together with the caption: “Sister bond, sister strength.”

On July 23, their family shared heartbreaking news: Katelyn had passed away.

“It is with heavy hearts that we announce the passing of our beloved Katie Bug (Katelyn Harding),” the family wrote. “After a 2 year battle with cancer (Osteosarcoma), Katie Bug has left us peacefully surrounded by her closest of family. At the young age of 20yrs old Katie touched countless hearts and brought a smile with everyone she met. She now rests in peace and is not alone as she has joined her mother (Devorah Sorger).”