5 things you may not know about breast cancer
AN APPLE A DAY - Tyrone M. Reyes M.D. (The Philippine Star) - October 5, 2015 - 10:00am

The Philippines has the highest incidence of breast cancer in Asia with one in every 13 Filipino women expected to develop breast cancer in her lifetime.  It has also registered the highest increase of 589 percent among 187 countries over a 30-year period from 1980 to 2010.  Furthermore, the Philippines registered the lowest survival rate for breast cancer among 15 countries surveyed in that same period.

Unlike heart attacks or strokes or diabetes, breast cancer seems to strike women who have no obvious risk factors.  “That’s one reason it’s so frustrating, especially to younger premenopausal women who have breast cancer,” says Walter Willett of the Harvard School of Public Health.  “They say, ‘I’m doing everything right,’ and they are.  Being health-conscious does not seem to prevent breast cancer.” Nevertheless, the disease is not a total mystery.  There are ways to lower your risk.  But misunderstanding abounds.  Here’s what you may not know.

1. GENES PLAY A SMALL ROLE IN MOST WOMEN.

Some call it the “Angelina effect.” Since May 2013, when actress Angelina Jolie announced she had double mastectomy to lower her risk of breast cancer, doctors saw a jump in the number of women getting tested for genes that cause the disease.

Jolie had good reason to get tested: Her mother had breast cancer and died of ovarian cancer at age 56, her grandmother died of ovarian cancer at age 45, and her aunt died of breast cancer at age 61, shortly after Jolie announced her mastectomy. 

The US Preventive Services Task Force doesn’t recommend that all women get tested, because most don’t have the genes that make a big difference in risk. “Two types of genetic susceptibility variants affect risk,” says David Hunter, the Vincent L. Gregory professor in cancer prevention at the Harvard School of Public Health. “First, there are the BRCA1 and BRCA2 mutations, which increase the risk of breast cancer twentyfold or more.”

The BRCA mutations — Jolie has BRCA1 — account for about five to 10 percent of breast cancers (and 10 to 15 percent of ovarian cancers). They’re broken versions of the genes for building proteins that prevent tumors by repairing the damaged DNA. The second type of genetic susceptibility variants increases the risk of breast cancer by only 10 to 20 percent.  “We now have a catalogue of over 100 so-called low-risk variants,” says Hunter. These variants seem to regulate how cells change as we grow and develop.  Scientists have not found signs that environmental factors are involved with these carcinogen-metabolizing genes.

2. EXTRA WEIGHT MATTERS.

If you’re postmenopausal, extra pounds boost your risk of breast cancer.  And it doesn’t have to be many pounds.  “It’s not just obesity,” notes Regina Ziegler, senior investigator at the US National Cancer Institute.  “Postmenopausal women who are overweight have a higher risk than those who are of normal weight.”

How does extra pounds promote postmenopausal breast cancer?  After menopause, a woman’s ovaries stop producing estrogen.  At that point, most of her estrogen is made by fat cells.  So the more fat cells she has, the higher her blood levels of estrogen — which travels to the blood as estradiol. “Women who are obese have about three times the circulating levels of estradiol compared to lean women,” says Willett.  “That’s a huge difference.  And we see some increase in risk even in women who gain five to 10 pounds.  It’s not just women who gain 50 or 60 pounds.”  What’s more, extra pounds may increase the risk of recurrence in women who have had breast cancer, according to the American Cancer Society.

Roughly 80 percent of breast tumors are hormone-receptor positive — that is, they are fueled by estrogen and/or progesterone.  Those tumors are usually easier to treat — with drugs that block estrogen production — than tumors that are not fueled by these hormones.

3. ALCOHOL BOOSTS RISK.

 “Alcohol is related to both premenopausal and postmenopausal breast cancer,” says Willett. “And the more you drink, the higher your risk.... For women who started drinking earlier in life and then stop, their risk goes down,” Willett explains. The highest risk is in women who started consuming alcohol early.

And it’s not just women who overdo it.  “We now see a 17-percent increased risk with only one drink every other day,” notes Willett.  “What’s remarkable is how modest that amount is.  With colorectal cancer, you don’t see much increase in risk until you get to over two drinks a day.”

Alcohol’s ability to raise blood estrogen levels appears to explain at least part of the increased risk.  “But we’re still not entirely sure whether it’s limited to the increase in estrogen or whether there’s more to it than that,” adds Willett.

4. KEEP MOVING.

“More than 100 epidemiological studies have looked at the risk of breast cancer and physical activity,” says Heather Neilson, a Canadian exercise researcher at Alberta Health Services in Calgary.  “The majority have found that women who are the most physically active have a 10 to 25-percent lower risk than women who are the least physically active.”

Most studies have tracked postmenopausal women, but some have looked at younger women.  And others have looked at those who already have breast cancer.  “The evidence is growing that women have a lower risk of dying of breast cancer if they are more active after diagnosis,” notes Neilson.

Studies strongly imply that for overweight or obese postmenopausal women, most of the benefit of exercise comes from weight loss.  “Still, the epidemiological evidence that exercise lowers the risk of breast cancer is quite strong, so there’s probably something about physical activity that we don’t understand, or different pathways that we’re not measuring,” says Kristin Campbell, an associate professor of physical therapy at the University of British Columbia.

In the meantime, scientists recommend exercise, whether you lose weight or not.

5. BEWARE OF RADIATION FROM CT SCANS.

Studies in humans find little evidence that non-ionizing radiation — like microwaves or radio waves — is a cause of breast cancer, according to a report of the US Institute of Medicine.  But it did point a finger at another kind of radiation:  CT (also called CAT) scans.

“There’s been a large increase in medical imaging that involves ionizing radiation, particularly with CT scans,” says Harvard’s David Hunter.  That’s particularly because the imaging is so much better than it was 20 or 30 years ago.

“Nobody thinks that CT scans are a major driver of breast cancer rates in the United States,” adds Hunter.  “It’s just that here is a known carcinogen where the exposure has actually increased over time, even as the machines have in theory been made safer and become better regulated.”

Most people — including some doctors — don’t realize that in order to produce a 3-D image, a CT scan of the abdomen exposes the body to 400 times more radiation than an ordinary chest x-ray.

“The doses from mammograms are much lower,” says Hunter. (A virtual colonoscopy is a CT scan. An MRI causes no radiation exposure.)

And then there’s the possibility of errors. “There have been documented incidences of overdose,” notes Hunter. “Regulations probably need to be tighter, given the proliferation of these medicines.”

Hunter’s bottom line: “Nobody should be subjected to medical imaging using ionizing radiation without a good rationale for it.  If the situation is not urgent, women should ask about the risks and benefits of having the procedure.”

 

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