Just over three years ago, my son, Damon, now 12, was getting a hug from his mom when she noticed a lump on his left arm. She took him straight to an urgent care center. After an X-ray, they were sent to an emergency room.

That’s where they got the diagnosis: bone cancer. Damon was immediately transferred to a pediatric hospital, where we got a clear picture of what we were up against: osteosarcoma, a rare and aggressive a cancer...