Letrozole or tamoxifen co-administration during fertility preservation for patients affected by breast cancer

Do fertility preservation outcomes differ between newly diagnosed breast cancer patients stimulated with FSH and tamoxifen compared with FSH and Letrozole?

Retrospective cohort study of fertility preservation treatments in newly diagnosed breast cancer patients at two tertiary centres (2000-2022).

Patients that underwent 354 fertility preservation cycles participated in the study (n = 290): letrozole (n = 215) and tamoxifen (n = 139). Treatments with letrozole were associated with higher FSH dosages (3970 ± 2027 IU versus 2839 ± 1052 IU, P < 0.001) but were of shorter duration (9.7 versus 10.5 days, P < 0.001). The letrozole group achieved lower peak oestradiol levels (1508 ± 1242 pmol/l versus 8760 ± 5771 pmol/l, P < 0.001) and endometrial thickness (8.1 mm ± 2.4 versus 9.5 ± 2.6 mm, P < 0.001). Mean oocyte number retrieved per cycle was comparable between the groups (13.6 ± 11.7 with letrozole versus 14.7 ± 9.8 with tamoxifen, P = 0.06). In 122 patients taking letrozole and 46 patients taking tamoxifen who underwent strictly oocyte cryopreservation cycles, the mean number of cryopreserved oocytes per cycle was comparable (11 ± 8.4 versus 12.1 ± 7.9, P = 0.21). Similar results were obtained in embryo cryopreservation: letrozole (n = 71 cycles) versus tamoxifen (n = 76 cycles) (6.2 ± 7.1 versus 7.0 ± 5.3, respectively, P = 0.12). Oocyte maturation rates among strictly oocyte preservation cycles were comparable (86 ± 17% with letrozole versus 83 ± 14% with tamoxifen, P = 0.06), as were fertilization rates in embryo cryopreservation cycles (IVF: 62 ± 26% versus 63 ± 26%, P = 0.8; intracytoplasmic sperm injection: 71 ± 28% versus 76 ± 23%, P = 0.30) with letrozole and tamoxifen, respectively. Multivariate analysis, controlling for potential confounders showed no significant correlations between treatment type and the number of retrieved oocytes or maturation rates.

Letrozole or tamoxifen co-administration with FSH yielded similar number of retrieved and cryopreserved oocytes and embryos, as well as similar oocyte maturation and fertilization rates.