Gianluigi Taverna of Humanitas Research Hospital in Milan and colleagues took urine samples from 320 men with prostate cancer, and 357 without it. The men with cancer had all different stages of the disease, from very low-risk, slow-growing tumors, to cancer that had spread.

Some of the men in the non-prostate-cancer group had other diseases or conditions, including other types of cancer.

One of the dogs detected every single prostate cancer case, and only hit false positives — when it identified cancer when it wasn’t there — in 2 percent of cases. The other dog was almost as accurate.