26歳未満の乳房切除：身体的合併症のみ高確実性

26歳未満の性別不合を有する individuals に対する乳房切除術：系統的レビューとメタ分析

Authors: Anna Miroshnychenko, Yetiani M. Roldan, Sara Ibrahim, Chan Kulatunga-Moruzi, Kristen Dahlin, Steven Montante, Rachel Couban, Gordon Guyatt, Romina Brignardello-Petersen
Journal: Plastic and Reconstructive Surgery
Year: 2024
Source: doi.org/10.1097/prs.0000000000011734

Summary

This review gathered 39 studies on breast removal surgery for young people with gender distress and rated how trustworthy the evidence was. Nearly all only followed operated patients, with no comparison group. Only short-term surgical complications were rated high-quality evidence, and they were uncommon: no deaths, about 2% to 3% loss of the nipple or skin graft through tissue death, and about 5% thick scarring. For the results that matter most, such as gender distress, mental health, suicide attempts, quality of life and regret, the evidence was weak or very weak. One study did suggest people were about half as likely to self-harm after surgery. The authors call for better studies. The review shows the evidence is weak; it does not show that surgery fails to help. It was funded by SEGM, a group that urges caution, and surgeons have challenged its framing in published letters.

Key findings

レビューでは、2023年6月までを検索して39件の研究が見つかりました。グループを比較したのは3件、手術の前後で測定したのは2件だけで、残る34件は手術を受けた患者を記述しただけでした。
高品質のエビデンスは、手術の合併症の研究からのみ得られました。死亡はなく（5件の研究）、1,000人あたり約20人が組織の壊死により乳首または皮膚移植片を失い（13件の研究）、約10人が皮弁を失い（3件の研究）、約50人が厚い瘢痕を経験しました（12件の研究）。
手術とチェストバインディングを比較した2件の研究は、胸に関する性別への苦痛と、体や胸への満足度について、非常に弱いエビデンスを示しました。
手術と手術なしを比較した1件の研究は、苦痛と自殺未遂について非常に弱いエビデンスを、手術後に（自殺の意図のない）自傷をする可能性が約半分になるという弱いエビデンスを示しました。
生活の質、うつ病、自殺による死亡、胸への満足度、後悔は、主に比較群がなかったため、すべて非常に弱いエビデンスと評価されました。
他のメンタルヘルスの状態、苦痛が始まった年齢、性的指向によって結果が異なるかどうかの計画された確認はできず、自殺念慮、性機能、その後の手術は評価されませんでした。
著者らは、患者、外科医、ガイドラインの作成者、政策立案者に情報を提供するため、患者を時間の経過とともに追跡する研究と、倫理的に可能であれば無作為化試験を求めています。

Abstract

BACKGROUND: Gender dysphoria (GD) refers to psychological distress associated with the incongruence between one's sex and one's gender. In response to GD, birth-registered female patients may choose to undergo mastectomy. In this systematic review, the authors summarize and assess the certainty of the evidence about the effects of mastectomy. METHODS: We searched MEDLINE, Embase, PsycINFO, Social Sciences Abstracts, LGBTQ+ Source, and Sociological Abstracts through June 20, 2023. We included studies comparing mastectomy to no mastectomy in birth-registered patients younger than 26 years with GD. Outcomes of interest included psychological and psychiatric outcomes, and physical complications. Pairs of reviewers independently screened articles, abstracted data, and assessed risk of bias of the included studies. We performed meta-analysis and assessed the certainty of the evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. RESULTS: We included 39 studies. Observational studies (n = 2) comparing mastectomy to chest binding provided very low-certainty evidence for the outcome of GD. One observational study comparing mastectomy to no mastectomy provided very low-certainty evidence for the outcomes of global functioning and suicide attempts, and low-certainty evidence for the outcome nonsuicidal self-injury (adjusted OR, 0.47; 95% CI, 0.22 to 0.97). Before-and-after (n = 2) studies provided very low-certainty evidence for all outcomes. Evidence from case series (n = 34) studies ranged from high to very low certainty. CONCLUSIONS: Case series studies demonstrated high-certainty evidence for the outcomes of death, necrosis, and excessive scarring; however, these are limited in methodologic quality. In comparative and before-and-after studies, the evidence ranged from low to very low certainty.

Conclusion

The best available evidence reporting the effects of mastectomy in individuals with GD ranged from high to very low certainty. High certainty evidence in this SR was derived from case series studies only. High-certainty evidence from prospective cohort studies and, if ethical, randomized controlled trials, are needed to describe the short- and long-term effects of mastectomy in individuals with GD on mental health outcomes. Higher certainty evidence would be useful to individuals with GD considering chest masculinization; clinicians and surgeons involved in their care; guideline developers; and policy makers and stakeholders who make decisions about treatment related to GD.

Methodological limitations

Weak underlying studies: 34 of 39 studies only described operated patients, with no comparison group. So the review cannot estimate how surgery affects mental health, as the authors admit.
Strong evidence only for complications: The 'high-quality' findings are about short-term surgical complications. The authors say these studies are of limited quality and may not apply to the wider group of people with gender distress.
Funder involvement: The review was done under an agreement with SEGM, which urges caution in youth gender medicine. SEGM members helped design the research question, though the McMaster team says it alone did the analysis and drew the conclusions.
Weak evidence is not proof of no benefit: Weak evidence of mental health benefit means the benefit is uncertain, not absent. Critics argue this difference can be lost when the review is used in policy debates.
Surgeons challenged its framing: Armstrong, Morrison, Lee and Kuzon (Plast Reconstr Surg 2026;157:144e-145e) argued that randomised trials and comparisons with people who do not want surgery are unsuitable, that suicide is the wrong measure for a body-image operation, and that the review rated supportive recent studies too low. Kulatunga-Moruzi and Montante replied (Plast Reconstr Surg 2026;157:145e-147e) that the review takes no position on whether surgery should be offered.
Many patients older than the target age: Studies counted if the average age was under 26 (under 30 for complications). Ratings were lowered when fewer than 60% of people were in range, so many patients were older than the group of interest.
English-language studies only: Studies in other languages were left out, as the authors admit, though they do not expect this to change the conclusions.
No group-by-group checks: There was too little data to test whether results differ by other mental health conditions, when distress began, clinic versus community groups, or sexual orientation.
Some results not looked at: Suicidal thoughts, sexual function, repeat surgery, emotional and eating disorders, relationships and daily functioning were left out to keep the work manageable. No data were found on breathlessness, back pain, psychiatric hospital stays or drug and alcohol use.
A guessed number: Before-and-after changes relied on an assumed figure, because the studies did not report it. The authors checked that higher and lower guesses gave similar results.
Too short to see regret: Few studies followed people long enough to capture regret or detransition, so that evidence was rated very weak.
Search is out of date: The search ended in June 2023, so later studies are not included.

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