Cancer Center studies reveal link between pregnancy and breast cancer
Story by Michele Conklin, Photos by Glenn Asakawa
Megan Walbridge was too busy chasing after her 15-month-old toddler to give much thought to the lump under her arm. A quick call to her general practitioner to set up an appointment, then she was back at it—teaching Samuel baby sign language, helping him negotiate stairs, playing hide-and-go-seek and splashing in the sprinklers.
Her doctors agreed. Most likely a breast infection, they said; let’s keep an eye on it.
The changes came fast. Within days a “cord” had developed that ran from the lump to her nipple. Her breast started swelling. Within three weeks, her breast had tripled in size, grown hot and hard, and had the texture of an orange peel.
At 33, Walbridge was diagnosed with breast cancer. As if the diagnosis were not shocking enough, Walbridge soon learned that the greatest joy in her life—becoming a mother—had actually increased her chances of getting the disease.
Pregnancy and breastfeeding have long been thought to reduce a woman’s chance of getting breast cancer. But a research team at the University of Colorado Cancer Center is working to raise awareness that pregnancy actually increases the risk of breast cancer in women for up to 10 years or more after each pregnancy. This risk eventually goes away for women who have babies before they are 30, but it never quite disappears for the vast numbers of women who choose to have children in their 30s or 40s.
About 25,000 women under the age of 45 will be diagnosed with breast cancer in the United States this year. Up to half of those women will have breast cancer associated with a pregnancy within the past six years.
“We’re talking about a vital component of American society,” says Virginia Borges, MD, an oncologist at the CU Cancer Center who specializes in this area. “These are women with babies and young children at home. If we lose them, we lose a wife, a mother and a worker.”
Creating the right environment
Borges has partnered with Pepper Schedin, PhD, researcher and professor of medical oncology at the University of Colorado School of Medicine, to better understand pregnancy-associated breast cancer (PABC). Schedin was the first to identify that the process involved in returning breasts to their normal state after pregnancy or breastfeeding creates an environment ripe for cancer promotion.
During this process, called involution, the body uses wound healing mechanisms to kill milk-producing cells, similar to how the body removes damaged tissue after a cut.
“Wound healing is a good process, but tumor cells happen to love wound-like environments,” Schedin says. “This environment is not only more likely to grow tumors but also to cause metastases.”
Pregnancy-associated breast cancer can grow and spread more rapidly than breast cancer in women who have not had children. Some studies show that, on average, a woman diagnosed with breast cancer within two years of giving birth has a 40 percent 5-year survival rate, compared with a 70 percent rate in a woman who has not had a child prior to diagnosis.
“None of this is to say women shouldn’t get pregnant,” says Borges, an associate professor of medical oncology at the CU School of Medicine, and mother of two young sons. “Having children is a good thing. The point we would like to make is that care providers need to have this on their radar screens, and women need to be self advocates.”
Borges and Schedin are as warm as their first names, Ginger and Pepper, suggest. Their passion for helping young women with breast cancer led them five years ago to open the Young Women’s Breast Cancer Translational Program at the CU Cancer Center. The team there specializes in the diagnosis, treatment and research of breast cancer in women under the age of 40 with a special emphasis in pregnancy associated breast cancer. Today, the program treats about 100 young women annually.
On the day Megan Walbridge was diagnosed with Stage 3 inflammatory breast cancer, her surgeon, Rebecca Wiebe, MD, of Exempla Lutheran Medical Center, referred her to the CU program. Walbridge was seen the following day and started chemotherapy the next morning.
Walbridge started treatment just 24 days after first feeling the lump under her arm. Although the journey seemed agonizingly slow and frustrating to her, many women are not diagnosed for months or even longer. This is because the chance of breast cancer in these women is so slim that it can be easily overlooked. Indeed, even prominent organizations including the American Cancer Society and the National Cancer Institute do not yet list pregnancy as a risk factor for breast cancer.
“I feel very driven to tell my story because young women are not educated about this,” Walbridge says. “I honestly believed I didn’t have to worry about breast cancer since I don’t have a family history and I’ve lived a very healthy lifestyle all my life, eating organic food and hormone-free meats and dairy. I assumed I was doing everything right, so why worry.”
Megan underwent six rounds of chemotherapy treatment over the following 18 weeks. “They hit me with the toughest drugs they had,” she says. Her last round of chemotherapy was on Dec. 2, 2011, and she had a bilateral mastectomy on Dec. 30. Six weeks of daily radiation followed.
“We were in battle mode for seven months, just trying to survive and raise our son. Now it feels a little strange, kind of surreal to have it over,” she says.
While being pregnant raises the risk of breast cancer for all women, the risk is lower for younger women. Having a baby before age 30 increases the risk of breast cancer by 10 percent (and the risk to all women under 30 is extremely low already). That increased risk disappears over time and pregnancy eventually helps protect these women from breast cancer later in life.
The trend in the United States of women having babies when they are older increases the likelihood of more cases of pregnancy-associated breast cancer. The risk increases 30 percent if the mother is over the age of 35, and that increased risk never fully goes away.
“The probability of an individual woman getting breast cancer associated with her pregnancy is very low,” Schedin explains. “But it’s a low probability in a very big number of women. The sheer fact that five million women (per year in the US) are giving birth creates a societal problem.”
Schedin has become nationally renowned for the team’s work on pregnancy-associated breast cancer. Her hypothesis that cancer is aided by the involution process is being tested by labs around the world and, so far, seems to be holding up.
Last year, the team published a paper about the wound-healing effect in the American Journal of Pathology. In this study, they showed for the first time in humans that the natural processes of immune suppression and tissue inflammation during involution breeds cells that are friendly to cancer.
They are now looking at whether anti-inflammatories such as fish oil, aspirin or ibuprofen can help the body’s immune system fight this cancer-promoting effect.
In a pre-clinical study that is pending publication, the team found that giving ibuprofen to mice for two weeks during the involution process reduced the incidence of breast cancer, tumor size and metastases to the same levels as in mice that had never been pregnant.
Although a promising step, Borges and Schedin know they have years of work ahead of them to understand if the same effect can be achieved in women. They point to earlier studies of beta carotene and Vitamin E in lung cancer that were first thought to be cancer-fighting and were eventually shown to be cancer-promoting in some cases.
“With cancer, we’ve been wrong many times before,” Borges cautions. “What we can say absolutely is that pregnancy increases a woman’s risk of breast cancer and that women and their physicians need to be aware of that increased risk and take any changes in the breast seriously.”