Six years ago, I was diagnosed with appendix cancer, a very rare cancer diagnosed in less than 1,000 people in the U.S. each year.

It all began after a trail hike when I felt a tender pain in my lower right abdomen that wouldn’t go away. I went to my local doctor in Austin, Texas, and an ultrasound revealed a 6.5-cm tumor in my appendix. I had my appendix removed as part of a right hemicolectomy, and my lymph nodes tested negative...