Interrupting Endocrine Therapy to Attempt Pregnancy after Breast Cancer.

N Engl J Med

From the Department of Medical Oncology, Dana-Farber Cancer Institute (A.H.P.), Harvard Medical School (A.H.P., R.D.G.), the International Breast Cancer Study Group Statistical Center and the Department of Data Science, Division of Biostatistics, Dana-Farber Cancer Institute (S.M.N., R.D.G.), and Frontier Science and Technology Research Foundation and Harvard T.H. Chan School of Public Health (R.D.G.) - all in Boston; the International Breast Cancer Study Group (M.R., K. Ribi, R.K., G.V., A. Goldhirsch) and the Swiss Group for Clinical Cancer Research (O.P.), Bern, the Interdisciplinary Cancer Service Hospital Riviera-Chablais Rennaz, Geneva (O.P.), and University Hospitals, Lugano University, Lugano (O.P.) - all in Switzerland; the European Institute of Oncology, Scientific Institutes for Research, Hospitalization and Healthcare (IRCCS) (F.A.P., M.C., G.V., A. Goldhirsch), Milan; the Breast Cancer Center, Hospital Zambrano Hellion, School of Medicine, Tecnologico de Monterrey, San Pedro Garza Garcia, Mexico (H.A.A.); Vall d'Hebron University Hospital, Vall d'Hebron Institute of Oncology, and SOLTI Breast Cancer Research Group (C. Saura) and Soul Reconnect (T.F.), Barcelona, GEICAM Spanish Breast Cancer Research Group, Madrid (M.R.-B.), and Hospital Virgen del Rocio de Sevilla, Seville (M.R.-B.) - all in Spain; the Department of Breast and Medical Oncology, National Center for Global Health and Medicine (C. Shimizu), Breast Oncology Center, the Cancer Institute Hospital of the Japanese Foundation for Cancer Research (A.K.), and St. Luke's International Hospital, Breast Center (J.T.) - all in Tokyo; the Breast Cancer Unit, Department of Oncology, Division of Cancer Medicine, Oslo University Hospital, Oslo (A.B.S.); the Department of Medical Oncology, Leiden University Medical Center, Leiden (J.R.K.), and Antoni van Leeuwenhoek-Netherlands Cancer Institute, Amsterdam (F.A.) - both in the Netherlands; the Department of Medical Oncology, Centre Oscar Lambret, Lille (A.M.), and the Department of Surgery, Leon Berard Cancer Center, Centre Léon Bérard, Lyon (C.R.-J.) - both in France; Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto (E.W.); the Division of Medical Oncology, Department of Medicine, University of Colorado Cancer Center, Aurora (V.F.B.); the Department of Oncology, KU Leuven and Leuven Cancer Institute, and the Department of Obstetrics and Gynecology, University Hospitals Leuven, Leuven (F.A.), and Institut Jules Bordet and Université Libre de Bruxelles (A. Gombos, M.P.) and Breast International Group (S.E.-A.), Brussels - all in Belgium; the Division of Medical Oncology, Institute of Oncology, Ljubljana, Slovenia (S.B.); the Breast Division, Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, and the Department of Clinical Research and Evaluation, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University - both in Seoul, South Korea (J.E.L.); Cancer Trials Ireland, the Department of Medical Oncology, St. Vincent's University Hospital, and Tallaght University Hospital - all in Dublin (J.M.W.); the Breast Oncology Program, Cleveland Clinic Taussig Cancer Institute, Cleveland (H.C.F.M.); the Department of Surgery, Centre for Cancer Research, Melbourne Medical School, and the Royal Melbourne Hospital, University of Melbourne - both in Melbourne, VIC, Australia (C. Saunders); the Breast Unit, Helios University Hospital Wuppertal, University Witten-Herdecke, Wuppertal, Germany (V.B.-R.); the Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria (V.B.-R.); the Department of Medical Oncology, Institute for Oncology and Radiology of Serbia, Belgrade (S.S.); the Breast Unit, Champalimaud Clinical Center-Champalimaud Foundation, Lisbon, Portugal (F.C.); the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University, Baltimore (K.L.S.), and Breast Cancer and Melanoma Therapeutics, Cancer Therapy Evaluation Program, National Cancer Institute, Bethesda (L.A.K.) - both in Maryland; and the Department of Oncology, Mayo Clinic, Rochester, MN (K. Ruddy).

Published: May 2023

Background: Prospective data on the risk of recurrence among women with hormone receptor-positive early breast cancer who temporarily discontinue endocrine therapy to attempt pregnancy are lacking.

Methods: We conducted a single-group trial in which we evaluated the temporary interruption of adjuvant endocrine therapy to attempt pregnancy in young women with previous breast cancer. Eligible women 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. The primary end point was the number of breast cancer events (defined as local, regional, or distant recurrence of invasive breast cancer or new contralateral invasive breast cancer) during follow-up. The primary analysis was planned to be performed after 1600 patient-years of follow-up. The prespecified safety threshold was the occurrence of 46 breast cancer events during this period. Breast cancer outcomes in this treatment-interruption group were compared with those in an external control cohort consisting of women who would have met the entry criteria for the current trial.

Results: 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 1638 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.

Conclusions: Among 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 that in the external control cohort. Further follow-up is critical to inform longer-term safety. (Funded by ETOP IBCSG Partners Foundation and others; POSITIVE ClinicalTrials.gov number, NCT02308085.).

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10358451	PMC
http://dx.doi.org/10.1056/NEJMoa2212856	DOI Listing

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