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ホルモンを使うトランス女性は男性の46倍の乳がんリスク――それでも女性のリスクよりは低い、オランダのコホート研究

ホルモン治療を受けているトランスジェンダーの人々における乳がんリスク：オランダの全国コホート研究

コホート研究とレジストリ研究性別適合ホルモン療法
Authors
Christel J.M. de Blok, Chantal M. Wiepjes, Nienke M. Nota, Klaartje van Engelen, Muriel A. Adank, Koen M.A. Dreijerink, Ellis Barbé, Inge R.H.M. Konings, Martin den Heijer
Journal
BMJ
Year
2019
Source
https://doi.org/10.1136/bmj.l1652

Summary

Researchers used records from the Amsterdam gender clinic, which treats over 95% of Dutch transgender patients, linked to the national record of cancer diagnoses. They counted breast cancers in about 3,500 people on cross-sex hormones. Trans women got breast cancer far more often than men normally do (about 46 times), but still less often than women. Their tumours looked like the typical hormone-sensitive breast cancers seen in women. This suggests estrogen, and possibly the testosterone-blocking drug cyproterone acetate, shifts risk toward the female pattern. Trans men had a lower risk than women, likely helped by having had their breasts removed. The authors concluded the overall risk is low and normal screening is enough. With only 15 and 4 cases, missing data on major risk factors, and comparisons with the general population, the numbers are rough.

Key findings

  • この研究は、ホルモン治療を受けたトランス女性2,260人とトランス男性1,229人を追跡し、追跡期間はそれぞれ約34,000人年と15,000人年でした。
  • トランス女性には、典型的に18年（範囲7～37年）のホルモン使用の後、典型的には50歳で、15件の乳がんがありました。
  • 乳がんは、トランス女性では男性の約46倍多く（おそらく27倍から75倍の間）、ただし女性の約3分の1でした。
  • トランス女性の腫瘍の大半は、通常女性に見られるのと同じ、ホルモン感受性のタイプでした（83%がエストロゲン、67%がプロゲステロンによって成長）。
  • トランス男性には4件の乳がんがあり、女性の約5分の1の割合で、男性の59倍でした。3件は乳房切除の数年後に起こりました。
  • 治療法が頻繁に変わり、大半のトランス女性が酢酸シプロテロンを使っていたため、研究者は異なるホルモン薬を比較できませんでした。
  • 著者らは、ホルモンを使用しているトランスジェンダーの人々には、通常の乳がん検診の規則で十分だと結論づけました。

Abstract

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.

Conclusion

This large nationwide cohort study in the Netherlands showed an increased risk of breast cancer in trans women compared with cisgender men. The risk in trans women is still lower than in Dutch cisgender women and resembles a more female type of breast cancer and hormone receptor status. In trans men, a lower risk compared with Dutch cisgender women was observed. Based on this study, we conclude that the absolute overall risk of breast cancer in transgender people remains low and therefore it seems sufficient for transgender people using hormone treatment to follow screening guidelines as for cisgender people. As the risk of breast cancer in trans women increased during a relatively short duration of hormone treatment, it would be worthwhile for future studies to investigate in more detail the cause of breast cancer in transgender people receiving hormone treatment.