Increased Risk of Recurrence After Hormone Replacement Therapy in Breast Cancer Survivors

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Increased Risk of Recurrence After Hormone Replacement Therapy in Breast Cancer Survivors

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<nobr>Lars Holmberg</nobr>, <nobr>Ole-Erik Iversen</nobr>, <nobr>Carl Magnus Rudenstam</nobr>, <nobr>Mats Hammar</nobr>, <nobr>Eero Kumpulainen</nobr>, <nobr>Janusz Jaskiewicz</nobr>, <nobr>Jacek Jassem</nobr>, <nobr>Daria Dobaczewska</nobr>, <nobr>Hans E. Fjosne</nobr>, <nobr>Octavio Peralta</nobr>, <nobr>Rodrigo Arriagada</nobr>, <nobr>Marit Holmqvist</nobr>, <nobr>Johanna Maenpa</nobr>
On behalf of the HABITS Study Group [SIZE=-1]

Affiliations of authors: Department of Surgical Sciences, Uppsala University, Uppsala, Sweden (LH, M. Holmqvist); Regional Oncologic Center, Uppsala, Sweden (LH, M. Holmqvist); King’s College London, School of Medicine, Division of Cancer Studies, London, UK (LH); Department of Obstetrics and Gynecology, University Hospital and Institute of Clinical Medicine, Bergen University, Bergen, Norway (OEI); International Breast Cancer Study Group Coordination Center, Bern, Switzerland (CMR); Division of Obstetrics and Gynecology, Department of Molecular and Clinical Medicine, Faculty of Health Sciences, Linköping, Sweden (M. Hammar); Department of Oncology and Radiotherapy, Kuopio University Hospital, Kuopio, Finland (EK); Departments of Oncology and Radiotherapy (J. Jassem) and Plastic and Reconstruction Surgery (J. Jaskiewicz, DD), Medical University of Gdansk, Gdansk, Poland; Department of Surgery, St Olavs University Hospital, Trondheim, Norway (HEF); Chilean Oncology Research Cooperative Group, Santiago, Chile (OP, RA); Karolinska Institute, Stockholm, Sweden (RA); Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Tampere University Hospital, Tampere, Finland (JM) [/SIZE]
[SIZE=-1] Correspondence to: Lars Holmberg, MD, PhD, King's College London, School of Medicine, Division of Cancer Studies, 3rd Floor, Bermondsey Wing, Guy's Hospital, London SE1 9RT, UK (e-mail: lars.holmberg@kcl.ac.uk<script type="text/javascript"><!-- var u = "lars.holmberg", d = "kcl.ac.uk"; document.getElementById("em0").innerHTML = '<a href="mailto:' + u + '@' + d + '">' + u + '@' + d + '<\/a>'//--></script>).[/SIZE]
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Background: Hormone replacement therapy (HT) is known to increase the riskof breast cancer in healthy women, but its effect on breastcancer risk in breast cancer survivors is less clear. The randomizedHABITS study, which compared HT for menopausal symptoms withbest management without hormones among women with previouslytreated breast cancer, was stopped early due to suspicions ofan increased risk of new breast cancer events following HT.We present results after extended follow-up.<sup>

</sup> Methods: HABITS was a randomized, non–placebo-controlled noninferioritytrial that aimed to be at a power of 80% to detect a 36% increasein the hazard ratio (HR) for a new breast cancer event followingHT. Cox models were used to estimate relative risks of a breastcancer event, the maximum likelihood method was used to calculate95% confidence intervals (CIs), and

² tests were used to assessstatistical significance, with all P values based on two-sidedtests. The absolute risk of a new breast cancer event was estimatedwith the cumulative incidence function. Most patients who receivedHT were prescribed continuous combined or sequential estradiolhemihydrate and norethisterone.

Results: Of the 447 women randomly assigned, 442 could be followed fora median of 4 years. Thirty-nine of the 221 women in the HTarm and 17 of the 221 women in the control arm experienced anew breast cancer event (HR = 2.4, 95% CI = 1.3 to 4.2). Cumulativeincidences at 5 years were 22.2% in the HT arm and 8.0% in thecontrol arm. By the end of follow-up, six women in the HT armhad died of breast cancer and six were alive with distant metastases.In the control arm, five women had died of breast cancer andfour had metastatic breast cancer (P = .51, log-rank test).

Conclusion: After extended follow-up, there was a clinically and statisticallysignificant increased risk of a new breast cancer event in survivorswho took HT.


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