The Veteran Affairs Normative Aging Study (NAS) is a 30-year study of 2,200 men as they age. These researchers obtained serum samples to run PSA tests from 97 NAS participants who had prostate cancer, and from 281 participants with benign prostatic hyperplasia (BPH) or enlarged prostate. The investigators found that the average age at tumor inception was almost 61 years, with an age range of approximately 49 to 73. There was a duration of pre-clinical prostate cancer of almost 10 years. At 50 years of age, the average PSA level was 2.4 ng/ml if the patient did not already have prostate cancer. After tumor inception, the average annual rate of increase in PSA level was 25.5% According to this study, these researchers believe a substantial portion of prostate cancer develops in the early 50's for patients, with the disease being diagnosed some 6.6 to 10 years later. They feel this information is important to developing optimal approaches to PSA screening for prostate cancer as men age.