Hormonal treatment and fertility
If your cancer is oestrogen sensitive (ER+), you will most likely be advised to undergo some form of hormonal treatment after your chemotherapy and radiotherapy has finished. This is usually in the form of tablets that work by blocking the effects of oestrogen on breast cancer cells so they cannot multiple. In pre-menopausal women the main agent used is tamoxifen.
Tamoxifen lowers the risk of recurrence in women with oestrogen receptor positive breast cancer. It blocks the effect of oestrogen in the breast tissue but can “encourage” the oestrogen effect elsewhere in the body which helps to explain its other actions/effects on the body. It can be prescribed for up to five years.
Tamoxifen is a great drug in your armoury against recurrence, but it is important to consider the relationship between it and fertility, especially if you are still hoping to conceive post-treatment.
- There is no conclusive evidence that Tamoxifen makes you menopausal, although this is currently being studied. It does however cause hot flushes.
- About 20% of women will have irregular periods on tamoxifen but only a few stop their cycles entirely. In general your periods should return once you stop taking tamoxifen. However, tamoxifen may mask the onset of natural menopause. It may be only when you finish taking it that you realize you have started your menopause.
- Tamoxifen is sometimes used as a fertility treatment. At high doses, tamoxifen stimulates ovulation. Even at the doses given for breast cancer treatment, tamoxifen can initially increase ovulation. As a result, your oncologist will discuss with you the importance of using barrier contraceptives while on treatment if you are a pre-menopausal woman.
- As a general rule, tamoxifen should not be used if you are pregnant. Studies have suggested that it may be harmful for the developing foetus. It may be confusing to hear that tamoxifen can be used as a fertility drug but that it’s harmful to developing embryos. As a fertility treatment, tamoxifen is used to stimulate the ovaries to obtain more eggs for ovulation. At this point, the eggs have not been fertilized yet. Tamoxifen does not damage fertilized eggs. AFTER the eggs are fertilized and become embryos, tamoxifen may have a harmful effect. So before you’re pregnant, tamoxifen is considered safe, but once you’re pregnant it is not.
- If you are fertile after your treatment finishes, there is no evidence to suggest that getting pregnant increases your risk of your cancer returning. However, it is advisable to wait two years after your treatment finishes before becoming pregnant. This is because the possibility of the cancer returning lessens over time so that the first two years after treatment is when your risk is greatest. If you are on hormone therapy, you will be recommended to remain on this treatment for five years. If you do not wish to wait five years to become pregnant, it is advisable to speak to your specialist and this.