I am an adventurous 65-year-old. I hike long distances and climb high altitudes. I have been an above-knee amputee since I was 29, but I have never let that slow me down.

In October 2011, I reached my goal of standing at the base of Mount Everest. I had my sights set on Mount Kilimanjaro next and started training for that as soon as I got home. But a diagnosis of non-Hodgkin lymphoma put that adventure on hold.

My non-Hodgkin...