health alert on mammograms that is sparking a big debate. We reported on the changing recommendations about when a woman should start to get them. Now, a major new study is raising a provocative... See More
health alert on mammograms that is sparking a big debate. We reported on the changing recommendations about when a woman should start to get them. Now, a major new study is raising a provocative question. Should women get mammograms at all? ABC's Mara schiavocampo has the new details. Reporter: They are some of our most powerful weapons in the war against breast cancer -- mammograms. But today, they're being questioned by one of the largest mammogram studies ever done, spanning a quarter of a century. Researchers in Canada divided 90,000 women between the ages of 40 and 59 into two groups. The first group got regular mammograms. The second group did not, instead receiving only physical breast exams. After being monitored for 25 years, researchers found there were 500 deaths in the mammogram group, and 505 deaths among those who got breast exams alone. In other words, women who had regular mammograms were just as likely to die from breast cancer as those who had no mammograms at all. To me, the message is loud and clear. It isn't screening that's helping women, it's better therapy and possibly increased awareness. Reporter: What's more, the study also found getting frequent mammograms can have a big downside, resulting in over-diagnosis 22% of the time, leading to some chemotherapy and surgery that are completely unnecessary. News of the study caused an uproar. Some doctors questioning the way the study was conducted. Others argue mammograms are still on of the best tools we have for early detection. Until we have a much more accurate test to screen for breast cancer, that's what we need to stay with. What I don't want women to do is throw their hands up over fear or confusion or desperation or panic and do nothing. Reporter: For cancer survivor Beth Shulman, the answer is clear. The 54-year-old got a double mastectomy after a routine mammogram caught an aggressive form of breast cancer last year. I'm 100% sure that it did save me. It gave me a second chance. Reporter: The American cancer society tonight told me they stand by mammograms. They're advice remains, women over 40 should still get one each year, still, they say they are reviewing all of this evidence including the new study and if needed, George, they'll issue new guidelines later this year. Also consult with your own doctor.
This transcript has been automatically generated and may not be 100% accurate.