When and How Should a Frozen Embryo Transfer Occur?

When is it safe to consider a pregnancy?

Data is limited about when it is safe to consider pregnancy after treatment for cancer.  This decision is usually made in close collaboration between the patient, the oncology team, and the fertility specialist. 

• One study looked at pregnancy outcomes and risk of recurrence in women who conceived after breast cancer diagnosis and treatment.  They found a survival benefit in women who waited at least 2 years after diagnosis to attempt conception¹. 
• In some cases, the team decides that waiting to consider pregnancy until the 5-year disease-free marker is prudent. 
  • In young women, or women who banked eggs or embryos prior to chemotherapy, this time-frame will not dramatically affect pregnancy rates. 
  • However, in women who will be in the late 30’s or 40’s when attempting conception (without banked eggs or embryos), five years may dramatically decrease chances of pregnancy.  In these cases, women should be counseled about the possible additional benefit of egg/embryo banking, even in cases when then do not require chemotherapy.

What protocol is best for frozen embryo transfers in women with hormone-sensitive cancers?

For women with hormone sensitive cancers, providers frequently have anxiety about using added hormones for a ‘controlled’ frozen embryo transfer cycle.  This seems counter-intuitive, since women are trying to conceive, thus beginning a 40 week deluge of estrogens and progesterone.  That being said, it is reasonable to consider proceeding with a ‘natural cycle’ FET, when appropriate.  A Cochrane review of protocols for FET showed insufficient data to support the use of one regimen vs. another in infertile women².  In cancer survivors, there is no data about the safety of FET in general, regardless of preparation protocol. 

Is she having regular menstrual cycles?

• In women having regular menstrual cycles, consider attempting a natural-cycle regimen.
• While there are no studies about how long to be off tamoxifen before conception, consider stopping tamoxifen at least 1-2 months before attempting cycle (at least one full menstrual bleed). 

Hormone sensitive cancers – Irregular or absent menstrual cycles:

• If her menses are absent or very irregular, it will be necessary to proceed with a controlled cycle, using supplemental estrogen and progesterone.
• Consider stopping tamoxifen at least 1 month before attempting cycle (at least one full menstrual bleed). 
• If there are concerns that she may have ovulatory function during the FET cycle, proceed with a GnRH-agonist down-regulation with added estrogen and later progesterone supplementation.  Ideally, start GnRH-agonist in the luteal phase to avoid a flare response, though this may be challenging if her cycles are irregular. 
• If she clearly has premature ovarian failure, consider estrogen and progesterone supplementation without GnRH-agonist.

Non-hormone sensitive cancers:

• FET regimen should not matter.