4月3日,，《內(nèi)科學年鑒》（Annals of Internal Medicine）雜志發(fā)表的一項研究結果表明,，乳房X線篩查可能與15%~25%的“過度診斷性”乳腺癌有關。哈佛公共衛(wèi)生學院的Mette Kalager博士介紹,，這與既往其他國家的研究結果一致,，后者報告的估計過度診斷率為0%~54%不等，隨機對照試驗報告的過度診斷率約為30%,。
這項挪威研究的結果進一步表明,，對非致死性癌癥的過度診斷和不必要的治療，會帶來不容忽視的倫理和臨床問題,，而且會使人懷疑是否有必要繼續(xù)開展乳房X線篩查,。
自從1996年開展政府資助的乳房X線篩查項目以來，這一篩查在挪威逐漸變得常見,，但各地的推廣進程并不一致,，經(jīng)過10年時間才實現(xiàn)了普遍推廣。自2005年以后,，挪威所有50~69歲女性均被建議每2年篩查1次,，其中約77%依從了這一建議。“推廣進程的不一致為研究者提供了機會,，得以比較開展和未開展篩查的地區(qū)的乳腺癌發(fā)病率和過度診斷情況,，并且使研究者可以用兩種方法進行評估。”
該研究中的過度診斷是指,，假如不接受篩查一生中都不會出現(xiàn)臨床癥狀的乳腺癌,。即乳腺癌永遠不會進展為臨床期，或者在乳腺癌出現(xiàn)臨床表現(xiàn)之前患者已死于其他原因,，因此這類患者獲得診斷和治療不會帶來任何生存益處,。
該研究的對象包括39,888例在1996~2005年期間被診斷為侵襲性乳腺癌的女性，其中27,238例診斷時年齡為50~79歲,。共有7,793例在開始常規(guī)篩查后獲得診斷,。
采用第一種估計方法的完全校正分析顯示，在乳房X線篩查中發(fā)現(xiàn)的乳腺癌病例中有15%~20%——即1,169~1,948例——屬于過度診斷,。采用第二種估計方法進行分析,，18%~25%的病例為過度診斷。因此,，總體過度診斷率為15%~25%,。
而且，進展期乳腺癌的比例隨著時間推移而逐漸下降,，篩查組與未篩查組降至同一水平,，而Ⅰ期乳腺癌的比例僅在篩查組女性中顯著增加。這一結果提示,，乳房X線篩查發(fā)現(xiàn)的乳腺癌幾乎均為早期,、低危腫瘤,。“我們的結果提示，晚期癌癥較少可能是患者更加警惕的結果,，而不是篩查本身的功勞,。”
華盛頓大學的Joann G. Elmore博士和哈佛醫(yī)學院的Suzanne W. Fletcher博士在隨刊述評中指出：“沒必要太糾結于過度診斷的確切范圍，當務之急是意識到任何程度的過度診斷都是嚴重的,，必須盡快解決這一問題,。”一種減少過度診斷的方法是，調(diào)整乳房X線檢查結果的“異常”閾值,。同時,，對于確定的病變可以建議繼續(xù)嚴密觀察而不必立即活檢(Ann. Intern. Med. 2012;156:536-7)。“我們有義務告知女性這種過度診斷現(xiàn)象,，而實際上多數(shù)患者教育都沒有提及這一問題,。”
Elmore博士在非營利性醫(yī)療決策告知基金會出版的患者教育材料中擔任了醫(yī)學編輯，F(xiàn)letcher博士報告稱從事乳腺癌篩查達36年之久,，并在1980年代早期為美國預防服務工作組提供了服務,。這項研究獲得了挪威前沿科學研究理事會的支持。Kalager博士及其合著者無利益沖突披露,。（生物谷Bioon.com）
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PMID:22473436
Overdiagnosis of Invasive Breast Cancer Due to Mammography Screening: Results From the Norwegian Screening Program
Mette Kalager, MD; Hans-Olov Adami, MD, PhD; Michael Bretthauer, MD, PhD; and Rulla M. Tamimi, ScD
Background: Precise quantification of overdiagnosis of breast cancer (defined as the percentage of cases of cancer that would not have become clinically apparent in a woman's lifetime without screening) due to mammography screening has been hampered by lack of valid comparison groups that identify incidence trends attributable to screening versus those due to temporal trends in incidence.
Objective: To estimate the percentage of overdiagnosis of breast cancer attributable to mammography screening.
Design: Comparison of invasive breast cancer incidence with and without screening.
Setting: A nationwide mammography screening program in Norway (inviting women aged 50 to 69 years), gradually implemented from 1996 to 2005.
Participants: The Norwegian female population.
Measurements: Concomitant incidence of invasive breast cancer from 1996 to 2005 in counties where the screening program was implemented compared with that in counties where the program was not yet implemented. To adjust for changes in temporal trends in breast cancer incidence, incidence rates during the preceding decade were also examined. The percentage of overdiagnosis was calculated by accounting for the expected decrease in incidence following cessation of screening after age 69 years (approach 1) and by comparing incidence in the current screening group with incidence among women 2 and 5 years older in the historical screening groups, accounting for average lead time (approach 2).
Results: A total of 39 888 patients with invasive breast cancer were included, 7793 of whom were diagnosed after the screening program started. The estimated rate of overdiagnosis attributable to the program was 18% to 25% (P < 0.001) for approach 1 and 15% to 20% (P < 0.001) for approach 2. Thus, 15% to 25% of cases of cancer are overdiagnosed, translating to 6 to 10 women overdiagnosed for every 2500 women invited.
