Breast cancer risk in transgender people receiving hormone treatment: nationwide cohort study in the NetherlandsBMJ 2019; 365 doi: https://doi.org/10.1136/bmj.l1652 (Published 14 May 2019) Cite this as: BMJ 2019;365:l1652
- Christel J M de Blok, PhD candidate1 2,
- Chantal M Wiepjes, PhD candidate1 2,
- Nienke M Nota, PhD candidate1 2,
- Klaartje van Engelen, clinical geneticist3,
- Muriel A Adank, clinical geneticist4,
- Koen M A Dreijerink, endocrinologist1 2,
- Ellis Barbé, pathologist5,
- Inge R H M Konings, medical oncologist6,
- Martin den Heijer, professor in endocrinology and head of division1 2
- 1Centre of Expertise on Gender Dysphoria, Amsterdam UMC, VU University Medical Centre, Amsterdam, Netherlands
- 2Department of Endocrinology, Amsterdam UMC, VU University Medical Centre, Amsterdam, Netherlands
- 3Department of Clinical Genetics, Amsterdam UMC, VU University Medical Centre, Amsterdam, Netherlands
- 4Department of Clinical Genetics, Netherlands Cancer Institute, Amsterdam, Netherlands
- 5Department of Pathology, Amsterdam UMC, VU University Medical Centre, Amsterdam, Netherlands
- 6Department of Oncology, Amsterdam UMC, VU University Medical Centre, Amsterdam, Netherlands
- Correspondence to: M den Heijer, Department of Internal Medicine, Section Endocrinology, Amsterdam UMC, VU University Medical Centre, PO Box 7057, 1007 MB Amsterdam, Netherlands
- Accepted 27 March 2019
Objective To investigate the incidence and characteristics of breast cancer in transgender people in the Netherlands compared with the general Dutch population.
Design Retrospective, nationwide cohort study.
Setting Specialised tertiary gender clinic in Amsterdam, the Netherlands.
Participants 2260 adult trans women (male sex assigned at birth, female gender identity) and 1229 adult trans men (female sex assigned at birth, male gender identity) who received gender affirming hormone treatment.
Main outcome measures Incidence and characteristics (eg, histology, hormone receptor status) of breast cancer in transgender people.
Results The total person time in this cohort was 33 991 years for trans women and 14 883 years for trans men. In the 2260 trans women in the cohort, 15 cases of invasive breast cancer were identified (median duration of hormone treatment 18 years, range 7-37 years). This was 46-fold higher than in cisgender men (standardised incidence ratio 46.7, 95% confidence interval 27.2 to 75.4) but lower than in cisgender women (0.3, 0.2 to 0.4). Most tumours were of ductal origin and oestrogen and progesterone receptor positive, and 8.3% were human epidermal growth factor 2 (HER2) positive. In 1229 trans men, four cases of invasive breast cancer were identified (median duration of hormone treatment 15 years, range 2-17 years). This was lower than expected compared with cisgender women (standardised incidence ratio 0.2, 95% confidence interval 0.1 to 0.5).
Conclusions This study showed an increased risk of breast cancer in trans women compared with cisgender men, and a lower risk in trans men compared with cisgender women. In trans women, the risk of breast cancer increased during a relatively short duration of hormone treatment and the characteristics of the breast cancer resembled a more female pattern. These results suggest that breast cancer screening guidelines for cisgender people are sufficient for transgender people using hormone treatment.
Contributors: CdB, CW, NN, and MdH designed the study. CdB, CW, NN, KvE, EB, and MdH collected the data. CdB, CW, and NN analysed the data. CdB, CW, NN, KvE, MA, KD, EB, IK, and MdH interpreted the data. CdB drafted the manuscript. CdB, CW, NN, KvE, MA, KD, EB, IK, and MdH revised the manuscript and approved the final version. CdB and MdH are the guarantors. This manuscript is an honest, accurate, and transparent account of the study being reported and no important aspects of the study have been omitted. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: This study was reviewed by the ethical review board of the VU University Medical Centre Amsterdam. It was determined that the Medical Research Involving Human Subjects Act (WMO) does not apply to this study, and necessity for informed consent was waived. All data were processed anonymously.
Data sharing: Statistics Netherlands prohibit data sharing at an individual level to guarantee the anonymity of the people in its databases.
Transparency: The lead authors (CdB and MdH) affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.
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