Prostate cancer is one of the most common types of cancer in men. Most of the men who have it are over 65 and live active lives. If your oncologist (the type of doctor that sees cancer patients) sees that your cancer is growing slowly, they may decide that you don't need treatment. You should never make that decision by yourself.
If you were diagnosed with prostate cancer, you may hear your oncologist use terms such as "watchful waiting" or "active surveillance." These may come up if the cancer is determined to be small, slow-growing, and confined within the prostate (has not metastasized). Some doctors don't use the terms properly, so be sure that your oncologist has the right definition.