"In women who have had breast cancer annual mammograms help detect second breast cancers but theyre not as effective in women who have never had the disease new research suggests. Screening mammography does work well in women with a history of breast cancer so they should continue to get their annual screening mammogram said Diana Miglioretti senior investigator at Group Health Research Institute in Seattle and a coauthor of the new research. But they also need to remain vigilant because they are at increased risk of cancers not detected on mammography that show up between mammograms. In their study published in the Feb.  issue of the Journal of the American Medical Association Miglioretti and her colleagues found that false positives and interval cancers were both higher in women with a history of breast cancer than in those without such history. False positives are an initial finding of cancer that turns out to be benign based on additional testing. Interval cancers are those found between mammograms either through additional tests or symptoms. The researchers evaluated  years of data from  screening mammograms in  women with earlystage breast cancer and an equal number of mammograms in another  women who had never had breast cancer. The women were matched on such factors as age and breast density a risk factor for cancer with higher density increasing risk. Within a year of the screening  cancers were found in women with a breast cancer history and  in those without.  Mammograms had detected . percent of the cancers in women who had never had breast cancer and . percent in those who had previously had the disease. As for false positives  percent of the women without a history of breast cancer were referred for biopsy but ended up being cancerfree compared with . percent of those with a breast cancer history. The interval cancer rate was . per  screenings in those with a history and . per  in those without the investigators found.  Women with a history of breast cancer were also more likely to be called back for additional imaging or biopsies  percent called back compared with . percent of the others. I think its mostly positive news Miglioretti said. Of the ones that are missed most of them are early stage. It points to the need she said for women to remain vigilant about screening after their breast cancer treatment  and to report any symptoms to their doctor immediately. Dr. William Audeh medical director of the Samuel Oschin Cancer Center and the Wasserman Breast Cancer Risk Reduction Program at CedarsSinai Medical Center in Los Angeles described the findings as not at all surprising. He reviewed the study but was not involved in it. After surgery and radiation he said a womans breasts have changed and there is a greater chance that a radiologist will think that something is abnormal simply because of the changes. That helps explain the false positives Audeh said. And though mammography did not catch all cancers in the women with a breast cancer history the study still points out the value of the test he said. Robert Smith director of cancer screening for the American Cancer Society agreed. Despite poorer performance compared with women without a prior history of breast cancer overall screening mammography was effective at detecting the majority of breast cancer in women with a history at an early favorable stage with the majority of tumors being diagnosed as ductal carcinoma in situ or stage  Smith said. A trend among cancer specialists Audeh said is to tailor followup for a woman who has had breast cancer. For those who have dense breasts and are younger than  for example we can alternate mammograms with breast MRIs with one of the tests every six months he said. More information WomensHealth.gov has more on mammograms httpwomenshealth.govfaqmammograms.cfm. SOURCES Diana Miglioretti Ph.D. senior investigator Group Health Research Institute Seattle William Audeh M.D. medical oncologist and medical director Samuel Oschin Cancer Center and Wasserman Breast Cancer Risk Reduction Program CedarsSinai Medical Center Los Angeles Robert A. Smith Ph.D. director cancer screening American Cancer Society Atlanta Feb.   Journal of the American Medical Association"