マンモグラフィーで乳癌死亡率を下げることはできない・・のか？

年一回のマンモグラフィーでは乳癌死亡率を下げることはできないという報告がNEJMに引き続いてBritish Medical Journalに掲載された。この論文はopen accessなので誰でも読める。

2012年のNEJMの論文とはこれだ。
☆☆☆☆☆☆☆☆☆☆☆☆

2012年11月23日金曜日

マンモグラフィーの微妙な位置づけ：最新のNEJM

N Engl J Med 2012; 367:1998-2005
November 22, 2012

Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence 

Archie Bleyer, M.D., and H. Gilbert Welch, M.D., M.P.H.

☆☆☆☆☆☆☆☆☆☆☆☆

小生はマンモグラフィーでの乳がん検診にはむしろ積極的に関わっているのが現状であり、このシステムを早々に放棄するつもりはないが、日本のマンモグラフィーの扱いが・・・

1. 日本では今後の乳癌検診では「触診」＋「マンモ」をやめて「マンモグラフィ−」一本で行こうというのが流れのようだが、それには、附随発生する可能性のある「過剰診断」リスクを、どう織り込んでいくのかが課題であろう。当論文にあるようにマンモグラフィ−を受けた424人のうち一人の割合で「乳癌」との過剰診断を受けることになるわけだから。
   
   
2. ただし 「過剰診断」リスクというのはどんな検診にもつきものである。私たちが最終的な目標とする「日本の乳癌死亡数減少」に「日本」の「マンモグラフィ−検診」が貢献できるのかは、医学的はもちろんのこと、科学的（必ずしも統計的とはいわないが）にも、医療経済学的にも充分議論を尽くしてもらいたいところである。
   
   
3. 日本のマンモ受診率はいいところ18％というのが現状であろう。欧米並みにこれを上げたい、上げることが日本の乳癌死亡を減らすことだと皆さん頑張ってきたのだし、マンモ検診の精度を上げることにも努力が注がれてきた。でもこれでいいのか、私のようなperipheralにいる医者はちと悩んでいる。
   
   
4.  日本の乳癌専門医には1人1人がきちんとした考えを持って頂きたいと思う。そして学会としての態度は一定であるべきだ。マスコミや雑誌でこの件について発言するときは、ある程度は統一した考えで臨んでもらいたいと思う。混乱は絶対に困る。

Research

Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial

BMJ 2014; 348 (Published 11 February 2014)

Cite this as: BMJ 2014;348:g366

Correspondence to: A B Miller ab.miller@utoronto.ca 

Accepted 16 January 2014

 

Anthony B Miller, professor emeritus 1,Claus Wall, data manager 1,Cornelia J Baines, professor emerita 1,Ping Sun, statistician 2,Teresa To, senior scientist 3,Steven A Narod, professor 1,2

1. ¹Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario M5T 3M7, Canada
2. ²Women’s College Research Institute, Women’s College Hospital, Toronto, Ontario M5G 1N8, Canada
3. ³Child Health Evaluative Services, The Hospital for Sick Children, Toronto, Ontario, Canada

活発な議論がBMJのHP上で繰り広げられている。現段階(2/19)で22報の質疑応答が掲載。

Abstract

Objective To compare breast cancer incidence and mortality up to 25 years in women aged 40-59 who did or did not undergo mammography screening.

Design Follow-up of randomised screening trial by centre coordinators, the study’s central office, and linkage to cancer registries and vital statistics databases.

Setting 15 screening centres in six Canadian provinces,1980-85 (Nova Scotia, Quebec, Ontario, Manitoba, Alberta, and British Columbia).

Participants 89 835 women, aged 40-59, randomly assigned to mammography (five annual mammography screens) or control (no mammography).

Interventions Women aged 40-49 in the mammography arm and all women aged 50-59 in both arms received annual physical breast examinations. Women aged 40-49 in the control arm received a single examination followed by usual care in the community.

Main outcome measure Deaths from breast cancer.

Results During the five year screening period, 666 invasive breast cancers were diagnosed in the mammography arm (n=44 925 participants) and 524 in the controls (n=44 910), and of these, 180 women in the mammography arm and 171 women in the control arm died of breast cancer during the 25 year follow-up period. The overall hazard ratio for death from breast cancer diagnosed during the screening period associated with mammography was 1.05 (95% confidence interval 0.85 to 1.30). The findings for women aged 40-49 and 50-59 were almost identical. During the entire study period, 3250 women in the mammography arm and 3133 in the control arm had a diagnosis of breast cancer, and 500 and 505, respectively, died of breast cancer. Thus the cumulative mortality from breast cancer was similar between women in the mammography arm and in the control arm (hazard ratio 0.99, 95% confidence interval 0.88 to 1.12). After 15 years of follow-up a residual excess of 106 cancers was observed in the mammography arm, attributable to over-diagnosis.

Conclusion Annual mammography in women aged 40-59 does not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available. Overall, 22% (106/484) of screen detected invasive breast cancers were over-diagnosed, representing one over-diagnosed breast cancer for every 424 women who received mammography screening in the trial.