Tamoxifen or letrozole versus standard methods for women with breast cancer who freeze egg cells or embryos


Breast cancer treatment can cause infertility. Freezing egg cells (oocytes) or embryos before treatment can increase the chances of future motherhood. Hormonal treatment is required before freezing of oocytes or embryos. In cases of hormone-sensitive breast cancer, this hormonal treatment can theoretically be harmful. Therefore, these women may receive tamoxifen or letrozole in addition to standard hormonal treatment. Cochrane review authors examined the evidence about tamoxifen or letrozole versus standard methods for women with estrogen-receptor positive breast cancer undergoing freezing of oocytes or embryos in assisted reproduction.

Key results

No randomised studies were found in which the different types of treatment available for these women were compared. The evidence is current to October 2013.

Authors' conclusions: 

COS schedules with the additional use of tamoxifen or letrozole are commonly chosen as an alternative regimen in young women with ER positive breast cancer who undergo COS for oocyte or embryo cryopreservation. No randomised controlled trials support the idea that these alternative COS schedules are superior to standard COS.

Read the full abstract...

Cryopreservation of oocytes or embryos preceded by controlled ovarian stimulation (COS) can increase the chance of future pregnancy in women with breast cancer who risk therapy-induced ovarian failure. In women with estrogen-receptor (ER) positive breast cancer, alternative COS protocols with tamoxifen or letrozole are being used to theoretically inhibit breast cancer growth during COS.


To assess the effects of tamoxifen or letrozole, in addition to standard COS protocols, on the breast cancer-free interval in premenopausal women with ER positive breast cancer who undergo COS for embryo or oocyte cryopreservation.

Search strategy: 

We searched the Ovid Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE, Ovid EMBASE, Ovid PsycINFO, and EBSCOhost CINAHL. We applied no limitations in year of publication or language. In addition, we searched trial registers for ongoing and registered trials, conference abstracts, and sources of grey literature. The search was conducted in January 2013.

Selection criteria: 

Randomised trials comparing different COS protocols in women with breast cancer were eligible for inclusion.

Data collection and analysis: 

Two review authors independently scanned the titles, abstracts, or both sections according to Cochrane guidelines. If data to include were provided, data extraction would have been independently performed by two review authors by using forms designed according to Cochrane guidelines.

Main results: 

No randomised controlled trials were found that met the inclusion criteria.