When E! News anchor Giuliana Rancic announced on Monday that she is battling breast cancer, she said her cancer had been spotted by a mammogram ordered by her fertility specialist. As fans of the reality show Giuliana & Bill know, Rancic and her husband, Bill, have been trying to get pregnant through in-vitro fertilization (IVF). Immediately upon Rancic’s announcement women began asking, Can IVF contribute to breast cancer?
Rancic, who is just 36, told Ann Curry on Today that her doctor said: “I don’t care if you’re 26, 36, but I will not get you pregnant if possibly there is a small risk you have cancer, because if you get pregnant it can accelerate the cancer. All the hormones will accelerate the cancer.”
It’s a reasonable concern, given that women who undergo fertility treatments are exposed to unnaturally high levels of hormones, including estrogen and progesterone, often repeatedly. Previous data have suggested that these fertility drugs may be associated with increased risk for breast, uterine and ovarian cancers.
But, based on the best evidence, there is no clear link has been between IVF and breast cancer, experts say. Reported CNN’s medical managing editor Miriam Falco:
“There’s no evidence for a link between breast cancer and infertility treatment,” says Dr. Eric Widra, who chairs the Society for Assisted Reproductive Technology. A 2005 study looked at a possibility but the study authors concluded a link to breast or ovarian cancer had not been found.
Dr. George Sledge, co-director of breast cancer treatment at Indiana University’s Simon Cancer Center, says there are no good data to show that IVF accelerates breast cancer. “Not having a child and infertility in itself increases the risk for breast cancer,” he says. Sledge isn’t familiar with Rancic’s medical history, but he says the younger you are when you have your first child, the less likely you are to have breast cancer.
Last year, a large Swedish study found that rates of certain cancers were actually lower in women who underwent IVF, compared with those who conceived the old-fashioned way. That study involved 24,058 women who had children through IVF and 1.4 million Swedish mothers who did not require fertility treatment. Those who underwent IVF had a 24% lower risk of breast cancer and a 39% lower risk of cervical cancer, compared with women who never used IVF, over the eight-year follow-up.
The question is, Which comes first, the cancer or the infertility? Reported Healthland’s Maia Szalavitz at the time:
[W]omen who underwent IVF started out with higher rates of cancer than those in the general population; the fact that these women were more likely to have been treated for cancer, which causes infertility, is probably why they sought IVF. This risk was especially elevated for ovarian cancer: in women seeking IVF the risk of ovarian cancer was nearly four times greater than in other mothers before conception. That is likely because the same problems that contribute to ovarian cancer may also produce infertility. “If you have an ovary that has a tendency to develop into cancer, it might also be poorly functioning reproductively,” says Dr. Bengt Kallen, professor emeritus at the University of Lund and lead author of the study.
The Swedish study did not find any increased risk of cancer in women undergoing IVF over age 30, compared with younger women. But it could not determine whether repeated cycles of IVF might affect cancer risk, nor did it track cancer risk in women who underwent IVF but didn’t get pregnant.
As for Rancic, she told Curry that she intends to resume fertility treatments after her cancer treatment, which doctors say is possible. Typically, women can try again after they have been disease-free for a certain amount of time — each patient’s path is different depending on her particular circumstances.
“It depends on your cancer, your age, what kind of cancer you have,” Dr. Mitch Rosen, director of the Fertility Preservation Center at the University of California, San Francisco, told CNN’s Falco.
If a woman has the type of breast tumor that is fueled by estrogen, she will need to take tamoxifen, or other hormone-disrupting drugs, for five years before trying again to get pregnant, Falco reported. If her cancer is not affected by estrogen, she may undergo surgery, radiation and chemo, and perhaps wait a year before pursuing IVF again.
Meredith Melnick is a reporter at TIME. Find her on Twitter at @MeredithCM. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME