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NEW YORK (Reuters Health) - Biopsies taken to diagnose prostate cancer commonly cause temporary erectile dysfunction and, in some cases, lingering urinary problems, according to a new study. The findings, reported in the Journal of Urology, highlight the fact that even the tests for diagnosing prostate cancer can have side effects.And men who are undergoing prostate biopsies -- as well as those considering prostate cancer screening -- should be aware of those risks, experts say. This is especially important for men facing the prospect of multiple biopsies, since the risk of side effects appears to be related to the number of needle sticks used.For the study, German researchers followed 198 men who had been randomly assigned to undergo one of three forms of biopsy to check for suspected prostate cancer: a standard biopsy, where a needle was used to take no more than 10 tissue samples; a 10-sample biopsy along with the use of a periprostatic nerve block to lessen any pain from the procedure; or a "saturation" biopsy, where 20 tissue samples were taken. Saturation biopsies may be done in some cases where the doctor suspects a man has a particularly elevated risk of having cancer -- such as a man who has had a negative biopsy in the past yet has persistently suspicious findings on PSA screening tests. Taking more tissue samples during the biopsy should increase the chances of finding any tumor.But all those needle sticks may come at a cost, the study found.Men who underwent saturation biopsies had the highest risk of developing lingering problems with urination, such as straining to pass urine and frequent nighttime trips to the bathroom. Of that group, 10 percent reported severe symptoms before the biopsy; that figure increased to 18 percent one week after the test, and to 29 percent 12 weeks afterward. Men who'd had a standard biopsy showed an increase in urinary symptoms only in the first week. The percentage reporting moderate symptoms increased from roughly 32 percent to 39 percent, and the proportion with severe symptoms rose from 18 percent to 20.5 percent. Among men who'd had a biopsy with nerve block, just 0.6 percent reported severe urinary symptoms before the test. That rose to 8 percent one week afterward, and to almost 17 percent by week 12 -- though that latter finding was not statistically significant, which means it could have been due to chance. When it came to erectile function, men in all three biopsy groups had more problems one week after the test. The side effect did, however, gradually decrease over time. Among men in both the standard biopsy and saturation-biopsy groups, just over half reported severe erectile dysfunction one week after the test -- up from around one-quarter before. In the nerve-block group, that rate rose from 11 percent to 39 percent. By week 12, the men's rates of erectile problems had declined to close to their baseline levels. The findings are "not unexpected," said Dr. Paul Schellhammer, a urologist at Sentara Health System/Eastern Virginia Medical School in Norfolk who was not involved in the research. However, he noted in an interview, there has been little study into the urinary and erectile side effects of prostate biopsies."This study begins to define the risks," said Schellhammer, who has studied the effects of prostate cancer treatment on men's sexual and urinary function.Men facing repeat biopsies over time -- whatever the type of biopsy -- should be particularly aware of the chances for side effects, Schellhammer told Reuters Health, since it appears that the greater the number of needle-sticks into the prostate, the greater the odds of lingering urinary problems.It is not clear from this study exactly why men undergoing saturation biopsy had a greater risk of longer term urinary symptoms, according to lead researcher Dr. Tobias Klein of Marienhospital Herne in Germany. But it is possible, he told Reuters Health in an email, that damage to the "neurovascular bundle" -- a complex of nerves and blood vessels close to the prostate -- plays a role. The fact that prostate biopsies carry some risks -- which, besides the ones seen in this study, include more-immediate problems like bleeding and infection -- also has implications for men considering prostate cancer screening, according to Schellhammer.Routine screening with PSA testing is controversial. The tests measure concentrations of prostate-specific antigen, a protein produced by the prostate gland whose blood levels generally rise when a prostate tumor is present; however, a relatively high PSA does not necessarily mean cancer, and a biopsy must be done to confirm. And those biopsies often turn out to be negative.In the current study, 40 percent of the men were found to have cancer after their prostate biopsy. Much of the concern about PSA testing revolves around the fact that prostate tumors are often slow-growing, and screening may result in many men being treated for cancers that would never have caused them problems. So those treatments -- with their risks of side effects like erectile dysfunction and urinary incontinence -- can do more harm than good for some men.But men should also be aware, Schellhammer said, that prostate biopsies can have side effects as well, and that can be considered when they are making decisions on PSA screening.He added that the findings are also relevant to men diagnosed with prostate cancer who choose "active surveillance" -- where the doctor does not immediately treat the cancer, but instead monitors its progression. That surveillance, Schellhammer noted, might include yearly biopsies.