New chemotherapy regimens and management options developed during the last 20 years have
yielded increased survival rates in cancer patients but they also cause side effects such as
premature ovarian failure and infertility due to their gonadotoxicity. Hormone therapy also
increases survival rates in breast cancer patients; tamoxifen, a selective estrogen receptor
modulator, has been proven to reduce the risk of recurrence and mortality due to breast
cancer when administered during 10 years.
The risk of premature ovarian failure depends not only on the gonadotoxicity of chemotherapy
but also on the age of the patient, therefore although tamoxifen is not gonadotoxic itself,
it can compromise fertility because of the long length of treatment and the subsequent delay
in childbearing.
On the other hand, tamoxifen is a drug that can be used in assisted reproduction techniques
to induce ovarian stimulation, therefore, the tamoxifen treatment followed by breast cancer
patients represent somehow a way of continuous ovarian stimulation. If viable oocytes could
be retrieved during the long-term hormonal treatment with tamoxifen, there will be an option
to use them to restore fertility afterwards.
STUDY DESIGN:
Patients included in the study who have normal menstrual periods will be monitored by
sonography (antral follicle count) and serum hormonal levels: E2 (oestradiol), P4
(progesterone), FSH (follicle stimulating hormone) and LH (luteinizing hormone) from the
second day of their cycle. Patients without spontaneous menstruations will perform periodic
visits every 15 days until images corresponding with antral follicle definition will be seen,
this will be considered day 2 of the cycle.
Follow-up of the antral follicles will be done with sonography and serum hormonal levels
according to the protocols of the investigators in vitro fertilization unit. When a follicle
of more than 18 mm is seen, 250 µg of hCG (human chorionic gonadotropin) will be administered
and 36 hours after, transvaginal oocyte retrieval will be performed. Oocyte and embryo
quality assessment will be performed according to morphological ASEBIR (association for the
study of reproduction biology) classification on day +2 and +3. Grade 1 and 2 embryos on day
+3 will be cryopreserved.
Patients requiring assisted reproduction technologies to get pregnant after completion of
their oncologic treatment will have their embryos thawed and subsequently transferred.
FOLLOW-UP:
During the time oocytes retrieved are being used or until the end of gestation in case the
patient become pregnant.
Bearing in mind that most of the patients in our center undergo 5 year of tamoxifen
treatment, it will be assumed a maximum follow-up of 6 years.