DEAR DR. ROACH: I am a healthy 79-year-old with a question about the blood thinner Xarelto. I take it for occasional atrial fibrillation. I hear that it can be dangerous. My doctors don’t seem worried, but I am. I have had rectal bleeding in the past, which wasn’t serious but was scary. I can’t take aspirin, so when I accidently took it in an over-the-counter cold medication, I threw up blood. Should I be worried about being on Xarelto? — E.H.

ANSWER: Xarelto has the same or somewhat lower risk of bleeding compared with warfarin (Coumadin), but it cannot be reversed in an emergency. Aspirin significantly increases bleeding risk when added to Xarelto (or warfarin, or any of the other newer anticoagulants).

Throwing up blood is potentially a medical emergency, and you should at least talk to, if not see, your doctor that same day. If you threw up more than just a little blood, you should be on your way to the emergency room.

The decision to take anticoagulation to prevent stroke in atrial fibrillation is based on your benefits weighed against your risks. Given a history of vomiting blood and rectal bleeding, I would have a long talk with your doctor before making a decision.

DEAR DR. ROACH: I’m confused. While it may be true that the majority of men having prostate cancer may never be bothered by it, what about the minority whose lives will be threatened by it? If they aren’t screened and treated, many will die. — G.F.

ANSWER: I had a professor in medical school, Dr. Larry Wood, who used to say, “If I have confused you, you’re probably paying attention.” You have identified a major issue with prostate cancer screening (and screening in general): If screening harms some but saves the lives of a few, is it worth doing? That answer may be different if you are coming from a public policy perspective versus an individual perspective.

Although we don’t know the exact numbers, it is estimated that about 47 men need to be treated for prostate cancer in order to save one life. Put another way, 46 out of 47 men are treated for prostate cancer, with its attendant risk of side effects, such as loss of sexual function and incontinence, without reducing their likelihood of dying of prostate cancer. We can’t predict with certainty whose prostate cancer is destined to kill them and whose is destined to be more indolent and slow-growing. The Gleason score, a measure of pathologic appearance of the cancer, helps, but it is not completely accurate.

Ninety percent of men with screening-detected prostate cancer elect to get it treated. Based on the many letters I get, all of them feel like they were the lucky ones to have had their lethal cancer removed — even if, statistically, most of them were not destined to die from prostate cancer.

Because it is likely that the harms of screening outweigh the benefits, the U.S. Preventive Service Task Force has recommended against prostate cancer screening in general. However, there are certainly cases in which I feel prostate cancer screening (remember that “screening” means that there are no symptoms or signs of cancer) is appropriate, which is why it’s important to have an individualized discussion of the risks and benefits of screening.

The booklet on the prostate gland discusses enlargement and cancer. Readers can obtain a copy by writing: Dr. Roach — No. 1001, 628 Virginia Dr., Orlando, FL 32803. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.