for females ages 18-50 (full criteria)
at San Francisco, California
study started
completion around
Principal Investigator
by Mitchell Rosen, MD
Headshot of Mitchell Rosen
Mitchell Rosen



Latrogenic infertility as a result of cancer treatment has a profound effect on long-term quality of life in survivors of reproductive-age cancers. Oocyte cryopreservation prior to cancer treatment has been associated with improved quality of life, with a potential ability to reduce long-term decision-related regret in cancer survivors. Though letrozole plus gonadotropin and and tamoxifen plus gonadotropin are currently routinely used worldwide in ovarian stimulation cycles for fertility preservation in patients with estrogen-receptor-positive breast cancer, it is not clear which of the two might lead to improved oocyte yield. Improved knowledge about the efficacy of these medications, with regard to oocyte yield, has the potential to significantly improve quality of life in reproductive-age breast cancer survivors.



Our primary objective is to determine whether concomitant administration of tamoxifen 20 mg oral with gonadotropins (tamoxifen-gonadotropin) versus a starting dose of letrozole 5 mg oral with gonadotropins (letrozole-gonadotropin) will result in a difference in mature oocyte yield during our routine ovarian stimulation protocol for fertility preservation for Estrogen-Receptor-Positive (ER+) breast cancer.

Specific Aims: Each of the following aims will include a primary comparison and secondary comparisons.

Primary aim: The primary aim will be to compare patients with ER+ breast cancer who are treated with letrozole-gonadotropin versus patients with ER+ breast cancer who are treated tamoxifen-gonadotropin with regard to ovarian stimulation outcomes.

  • Primary comparison:

    1) To determine if the assigned stimulation regimen will result in a difference in mature (meiosis II) oocyte yield in patients with breast cancer who undergo ovarian stimulation for fertility preservation.

  • Secondary comparison:
    1. To compare estrogen, progesterone, and androgen levels during the ovarian stimulation cycle.
    2. To compare estrogen, letrozole, and tamoxifen levels in follicular fluid.
    3. To compare duration of stimulation (days) and total gonadotropin dose (international units of FSH).
    4. To assess embryo quality, if applicable, on day 3 and day 5 of embryo culture, a measure of the developmental competence of the oocytes.
  • Experimental comparison:
    1. To compare clinical pregnancy rates when cryopreserved tissue is eventually utilized among patients from the assigned stimulation regimens. This comparison is labeled experimental because of the remoteness of such an outcome from our present study.

Secondary Aim: We will repeat the above comparisons among patients with ER+ breast cancer who are treated with tamoxifen-gonadotropin versus a prospectively-obtained reference group of patients with Estrogen-Receptor-Negative (ER-) breast cancer who are treated gonadotropin alone. We will then again repeat the above comparisons among patients with ER+ breast cancer who are treated letrozole-gonadotropin versus patients with ER- breast cancer who are treated gonadotropin alone.

Experimental Design and Methods:

Study population:

The target population is reproductive-age women who have been recently diagnosed with ER+ breast cancer and choose to undergo oocyte or embryo cryopreservation prior to chemotherapy treatment. All eligible women will be asked to join the study at their initial University of California, San Francisco (UCSF) fertility preservation consult. Study participants will be recruited from the Reproductive Endocrinology Clinic at University of California, San Francisco Center for Reproductive Health. A consecutive sample with ER- disease will also be recruited at the same type of visit. They will be asked to take part in the gonadotropin only stimulation group, which will be used for a secondary aim.


Infertility, Fertility Preservation, Breast Cancer, Tamoxifen, Letrozole, ER Positive - Letrozole, ER Positive - Tamoxifen, ER Negative


You can join if…

Open to females ages 18-50

  • New breast cancer diagnosis
  • Has not yet begun chemotherapy
  • Desires to undergo ovarian stimulation and oocyte retrieval prior to cancer treatment
  • Age 18 years old or greater

You CAN'T join if...

  • Chemotherapy has already commenced or been completed
  • History of recurrent breast cancer (with a prior history of chemotherapy)
  • Stage IV breast cancer diagnosis (metastases remote from the breast)
  • Patient's oncologist advises against the trial - in which case they can choose to receive stimulation with letrozole+gonadotropin
  • Does not plan to undergo ovarian stimulation and oocyte retrieval prior to diagnosis
  • Any significant concurrent disease, illness, or psychiatric disorder that would compromise patient safety or compliance, interfere with consent, study participation, follow-up, or interpretation of study results
  • Age less than 18 years old


  • University of California at San Francisco accepting new patients
    San Francisco California 94143 United States

Lead Scientist at UCSF

  • Mitchell Rosen, MD
    Dr. Mitchell Rosen is a reproductive endocrinology and fertility expert at the UCSF Center for Reproductive Health. He also is director of the UCSF Fertillity Preservation Center, which helps patients with cancer preserve their ability to have children, despite aggressive cancer treatment.


accepting new patients
Start Date
Completion Date
University of California, San Francisco
Phase 3 Infertility Research Study
Study Type
Expecting 144 study participants
Last Updated