Welcome to the Board, but I hope you won't have the results that would cause you to become a frequent participant.
A PSA increase is almost always due to one of three causes: benign growth, infection or inflammation, and prostate cancer, with prostate cancer as the least likely cause. In your case, as I think you are aware already, benign growth has been ruled out. There are several rules-of-thumb, based on research, for how much PSA should be expected from healthy prostate tissue (no infection, no cancer), and one rule is to multiply the prostate volume in cc by 0.066, or 16 X 0.066 = 1.056 in your case; another rule is to multiply the gland size by .1, which equals a PSA of 1.6 for you. Obviously, benign growth does not account for much of the PSA.
Your current PSA of 10 puts you in the area where prostate cancer is a possibility
, but the rise from 1 over the past four years also could be due to an infection, chronic or temporary. Infections can drive PSA really high, with 50 being quite possible and as high as 200 in rare instances.
The pattern of increase is often a valuable clue. Prostate cancer is usually distinguished by a constant time period for the PSA to double. In other words, it goes from, say, 1,000,000 cancer cells, which divide, into 2,000,000; then the 2,000,000 split into 4,000,000; the 4,000,000 into 8,000,000, and so on. This creates what is known mathematically as an exponential pattern of increase. If you graph it with enough points, it will look like a curve with a steadily accelerating rise. Sometimes the pattern is murkier because of PSA increasing at the same time due to benign growth, or affected by infection. In your case, benign growth would not mess up the curve much, so you are left with infection or prostate cancer. Increases due to infection are only exponential by chance; normally they will be uneven, often forming a see-saw up and down pattern. What does your pattern look like?
The absence of symptoms is good, but you can still have an ongoing infection or cancer.
A new test has been available for several years now that is not influenced by infection or benign growth. It is known by several names, but one name is the PCA3 test, or PCA3Plus test. It is a urine test; a sample is collected shortly after an intensive massage of the prostate for about a minute by the doctor. A low value on the test is a good but not perfect indicator that there is no cancer.
The "free PSA test" has been around for years, but, unfortunately, it can be fooled by infection and report a low value; then you aren't sure whether the result is due to infection or cancer. On the other hand, if you get a high value, say 25% or higher for strong confidence, it's likely you do not have cancer.
There's a new prostate cancer book from August of last year that is outstanding on many aspects of the disease, but it is especially good for patients and doctors trying to figure out whether the patient has cancer. Here's the title: "Invasion of the Prostate Snatchers -- No More Unnecessary Biopsies, Radical Treatment, or Loss of Sexual Potency", by Ralph H. Blum and Mark Scholz, MD. (The word "unnecessary" deserves emphasis; the authors are strongly in favor of treatment when it is
I hope this helps.