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Interrupting Endocrine Therapy to Attempt Pregnancy After Breast Cancer

In the POSITIVE trial of select women with previous hormone receptor–positive early breast cancer, temporary interruption of endocrine therapy to attempt pregnancy did not confer a greater short-term risk of breast cancer events, including distant recurrence, than in an external control cohort, researchers report. “Longer-term follow-up is needed to further inform the safety of this strategy,” the investigators conclude. “Nevertheless, these results provide an improved understanding of the effect of subsequent pregnancy on breast cancer outcomes in women.”

Eligible participants in the single-group trial were 42 years of age or younger; had had stage I, II, or III disease; had received adjuvant endocrine therapy for 18 to 30 months; and desired pregnancy. Following temporary interruption of adjuvant endocrine therapy, a primary endpoint of the number of breast cancer events (local, regional, or distant recurrence of invasive breast cancer or new contralateral invasive breast cancer) showed the following: “Among 516 women, the median age was 37 years, the median time from breast cancer diagnosis to enrollment was 29 months, and 93.4% had stage I or II disease. Among 497 women who were followed for pregnancy status, 368 (74.0%) had at least one pregnancy and 317 (63.8%) had at least one live birth. In total, 365 babies were born. At 1,638 patient-years of follow-up (median follow-up, 41 months), 44 patients had a breast cancer event, a result that did not exceed the safety threshold. The 3-year incidence of breast cancer events was 8.9% (95% confidence interval [CI], 6.3 to 11.6) in the treatment-interruption group and 9.2% (95% CI, 7.6 to 10.8) in the control cohort.”

Editorial: “Because having children remains a high priority for many young breast cancer survivors, some women will choose to pursue a pregnancy after a breast cancer diagnosis,” an editorialist writes. “The results of the POSITIVE trial provide the strongest evidence to date on the short-term safety of this choice. However, the enrolled patients were a selected cohort of women who were highly motivated to become pregnant. In addition, recurrences of breast cancer are reported to occur at a steady rate for up to 20 years after diagnosis among patients with hormone receptor–positive disease; the protocol-specified 10-year follow-up data will be essential to establish longer-term safety. Meanwhile, the POSITIVE trial provides prospective data showing that the temporary interruption of endocrine therapy to attempt pregnancy after hormone receptor–positive early breast cancer does not appear to increase the risk of recurrence or of contralateral breast cancer in the subsequent 3 years. Physicians should now incorporate these positive data into their shared decision-making process with patients.”

Source: New England Journal of Medicine