Will Chemotherapy Make You Infertile?

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“In general, all women with breast cancer who are in their reproductive years should be counseled regarding fertility preservation. Chemotherapy affects fertility in every woman, regardless of age. ”

Kutluk Oktay M.D.

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The answer to this crucial question depends on two things:

• Your age
  As every woman ages, her ovaries produce fewer fertile eggs. As you get closer to age 50 (on average), your ovaries make fewer and fewer fertile eggs until they stop making them altogether. That's when you go into menopause.
  Whether or not you have ovarian shutdown (also called ovarian failure, infertility, or premature menopause) after chemotherapy also has a lot to do with your age:
  • The younger you are, the more likely it is that your ovaries will still produce eggs after chemotherapy treatment.
  • The closer you are to the average age of menopause (51), the more likely it is that you will have permanent menopause and not be able to become pregnant after chemotherapy.
  • Once you reach age 35, you become more vulnerable to permanent ovarian shutdown after chemotherapy. This is particularly true after age 40.
• The types and doses of chemotherapy drugs you get
  We know that some chemotherapy drugs affect women's ability to become pregnant. But because research in this area is limited, it is often difficult to give an individual woman an accurate idea of her chance of keeping her fertility. Here's what we do know:
  • Early menopause brought on by chemotherapy may be temporary. In other words, your menstrual periods may stop and then start again after treatment is over. It can take a few months or as long as a year or more for your periods to return.
  • Women who receive relatively high overall doses of chemotherapy may be more likely to become permanently infertile than those on lower-dose regimens.
  • Some chemotherapy drugs, especially those that belong to a group called alkylating agents, can cause relatively more damage to the ovaries. As a result, they are associated with an increased risk of infertility. The most common example of this type of chemotherapy is cyclophosphamide (brand name: Cytoxan). Other chemotherapy drugs, including methotrexate, have been shown to have little effect on fertility.
    Here are common breast cancer chemotherapy drugs listed according to how much they affect fertility:
    • High risk of losing fertility: Cytoxan (chemical name: cyclophosphamide)
    • Medium risk of losing fertility: Platinol (chemical name: cisplatin) and Adriamycin (chemical name: doxorubicin)
    • Little or no risk of losing fertility: methotrexate (one brand name: Amethopterin), Adrucil (chemical name: 5-fluorouracil, fluorouracil or 5-FU), and vincristine (one brand name: Oncovin) 
  • Taxanes are a relatively new group of chemotherapy drugs that are proving to be very effective in treating breast cancer. They include Taxol (chemical name: paclitaxel) and Taxotere (chemical name: docetaxel). So far, there has been little research on how these drugs affect fertility. But from what has been found so far, they seem to belong to the low-risk group. It's important to remember that chemotherapy drugs are usually given in combination, not each one by itself. And when used in combination, their effect on fertility may be different. Also, the same drug may be given in different doses in different combinations. Talk with your doctor, a fertility expert, or both to learn about the potential risk of infertility with your treatment plan.
  • On average, about half of women under age 35 get their periods again after finishing chemotherapy treatment. But it's important to remember that for every individual woman the odds vary greatly, depending on the type and dose of treatment you get.
  • Women who have normal periods after chemotherapy may be able to get pregnant without difficulty. But some may still have trouble getting pregnant. This is because chemotherapy can damage the immature, or unripe, eggs in the ovaries. And research has shown that the lower the number of immature eggs in the ovaries, the earlier women go through menopause.
  • When you get your period back, it means that some eggs are maturing and ripening. But the number of eggs available for ripening may be much smaller than it would have been without the chemotherapy.
  • Because chemotherapy may cause birth defects, doctors advise you to use birth control carefully (but not birth-control pills) throughout treatment, so that you don't become pregnant during this time.
  • Chemotherapy may cause genetic damage to growing eggs. Even if you feel an urgency to get pregnant soon after chemotherapy, your doctors will advise you to wait. It's important to give your body at least six months or longer to recover from lingering side effects of treatment. Eggs that were exposed to chemotherapy need to repair themselves.
  • Ongoing research is looking at ovarian suppression to help protect women's eggs during chemotherapy. But right now this is highly controversial and should not be relied upon. (See section below.)

Ovarian suppression during chemotherapy

Ovarian function can be temporarily stopped, or suppressed, during chemotherapy by medication. Some believe this may help protect the immature eggs from damage during treatment. But there is a lot of disagreement among experts about this issue. So far there have been no reliable clinical studies on this issue.

Doctors are also concerned that the drugs used in ovarian suppression may interfere with chemotherapy's ability to kill the cancer cells. This is because chemotherapy is most effective against cancer cells when they're actively growing. Hormonal therapy — which is used to suppress the ovaries — can also stop or slow the growth of the breast cancer cells. This may make the cells less sensitive to chemotherapy.

The drugs used in ovarian suppression are called GnRH (gonadotropin-releasing hormone) agonists. They include Zoladex (chemical name: goserelin), Lupron (chemical name: leuprolide), and another drug called Trelstar (chemical name: triptorelin).

These medications block GnRH, a special hormone made in the brain that tells the ovaries to start getting ready for ovulation. Ovulation happens when a mature egg is released from the ovary, ready to be fertilized. When GnRH is blocked, no ovulation occurs.