A majority of doctors recommend regular mammograms for women, beginning at age 40.

Story highlights

Most women who get breast cancer have no family history

Mammograms are more important than self-exams, doctors say

Breast cancer is very treatable when caught early

Being overweight can increase your breast cancer risk

Health.com  — 

Few diseases stir up fear like breast cancer.

After all, one in eight women will get it in her lifetime: “We all know someone who’s had it,” says Dr. Barbara Levy, vice president for health policy for the American College of Obstetricians and Gynecologists (ACOG).

But just how scared should we be? And do we really know how to protect ourselves?

To find out, Health magazine — with ACOG’s help — conducted an exclusive survey of 753 readers and 1,248 OB-GYNs. What we found was startling: Even smart women like you have big misconceptions about this disease. Here’s what you think when it comes to breast cancer, what doctors want you to know — and the news that could save your life.

Surprise finding #1: 63% of women think family history is the biggest breast cancer risk factor.

What you should know: The vast majority of women with breast cancer have no family history.

In fact, aside from being female, your age is the biggest risk factor.

“As we get older, our tissue gets older, and the risk of developing disease increases,” says Dr. Susan Boolbol, chief of breast surgery at Beth Israel Medical Center in New York.

With age, we’ve also had more lifetime exposure to estrogen, which may boost breast cancer risk. This helps explain why your chance of being diagnosed jumps from 1 in 233 in your 30s to 1 in 29 in your 60s.

That said, there are simple ways to help protect yourself. And while age is a bigger risk factor, having a family history does up your chances of developing the disease, so be proactive.

Tell your doctor if a family member has had breast cancer (or even ovarian, prostate, or pancreatic cancers), so you can consider getting screened earlier, and discuss whether genetic testing or preventive medication might be good ideas for you.

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Surprise finding #2: 40% of women say breast cancer is the cancer they worry about most.

What you should know: Breast cancer is very treatable when caught early.

Though breast cancer is the most common cancer in women, lung cancer actually kills the most women every year. We have a 1 in 20 lifetime risk of dying from lung cancer, and a 1 in 36 lifetime risk of dying from breast cancer.

That’s because, compared with lung and other hard-to-treat cancers (such as ovarian), breast cancer tends to be caught at earlier, more treatable stages, thanks to screenings like mammograms (which is why it’s so important to get one every year, starting at age 40).

Why is breast cancer so feared then? It’s the disease we hear about the most through media coverage and fundraising efforts.

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Surprise finding #3: 39% of women say the most important way to catch breast cancer early is by doing a formal monthly breast self-exam (BSE). In other words, you think it is more crucial than mammograms.

What you should know: Mammograms are most important, 73% of docs say.

As for how often to get them, 85% of doctors advise beginning at 40 and going in every year or two after that.

Despite the U.S. Preventive Services Task Force’s 2009 recommendation that women start mammograms at age 50 (based on research suggesting there is a clearer benefit for older women), there’s still good reason to go in at 40: A 2010 study of about 600,000 women in their 40s found that receiving mammograms reduced their breast cancer death rate by 29%.

If you’re younger than 50, Levy suggests requesting a digital mammogram, which is better able to detect cancers in dense breasts (the kind that younger women tend to have).

Health.com: A complete guide to breast cancer screening

So why do women believe so much in BSEs? For years, our gynos, based on guidelines from major health institutions like the American Cancer Society (ACS) and ACOG, asked us to perform step-by-step, quadrant-by-quadrant self-exams at home to help us find potentially cancerous lumps between screenings.

But these groups have since stopped touting BSEs. Several studies have cast BSEs into doubt, including one showing no difference in death rates between women who were instructed to do self-exams and those who weren’t — plus, women who did them were more likely to get invasive, stress-inducing biopsies that found no cancer.

“Formal self-exams aren’t valuable,” Levy concludes. “Now we promote breast self-awareness — knowing how your breasts normally look and feel so if you notice a new lump or bump, you can bring it to your doctor’s attention.”

Rather than a monthly self-exam (which you may or may not remember to do), just feel your breasts from time to time while in the shower or in bed. If they usually feel like, say, sand, and one day you feel a rock, have your doctor take a look.

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Surprise finding #4: 4% of women say weight has the “biggest effect” on breast cancer risk.

What you should know: Being heavy increases your risk a whole lot — by as much as 40%.

So says one study that showed women who gained 20 to 30 pounds after age 18 had a higher risk of postmenopausal breast cancer than women who gained no more than five pounds. In fact, weight gain is a big enough risk factor that 78% of doctors polled recommend patients drop pounds to help fend off the disease.

It’s a message many of you are heeding: 32% of you say you’ve shed weight, and 57% exercise to lower your odds of getting the disease. Even going for brisk walks can reduce your risk, so start strolling and protect your breasts today.