Thompson says confusing symptoms of an enlarged prostate with signs of prostate cancer is a mistake a lot of men make.
"Now we know that they're generally unrelated," says Thompson.
Thompson conducted a historic decade-long study of almost 19,000 men and found no correlation between symptoms of an enlarged prostate and prostate cancer.
Thompson says the findings go against several national cancer groups, who urge men with urination troubles to get checked for prostate cancer.
Here's what the doctor says guys really need to know.
"Don't wait for urinary symptoms," says Thompson.
Thompson urges most men to talk with their doctor about prostate cancer around age 50. If it's in your family, or you're African-American, that conversation should start 10 years earlier.
Bottom line: Be proactive about your prostate before it's too late.
"The vast majority of cases of prostate cancer have no symptoms until they spread, until the cancer has spread," says Thompson.
Thompson says another study on the effects of certain vitamins and minerals on prostate cancer came back with some interesting results: Vitamin E slightly increased a man's risk for prostate cancer. And selenium increased the risk for diabetes.
Vitamin E and selenium can be found in men's supplements.