In 37 years as a police officer, Edwin Michel coped with a plane crash, a sniper, wildfires and three bullet wounds.
Nothing much rattled him until he was diagnosed with prostate cancer in November 2016. His doctor said the cancer wouldn’t kill him but Mr. Michel, now 76 years old, wasn’t entirely reassured. He felt more confident after a genomics test later revealed his prostate cancer was very low risk. The test, known as Oncotype DX, takes a sample from a prostate biopsy and analyzes 17 genes in it to estimate how aggressive...