乳房X光檢查加上超音波可幫助診斷有風險的婦女


  【24drs.com】根據包括2,662名緻密乳房且乳癌風險中度升高婦女進行的多中心研究,每年進行篩檢型乳房X光檢查加上超音波檢查,比單用乳房X光檢查多偵測34%的侵犯性乳癌。
  
  「American College of Radiology Imaging Network(ACRIN) 6666」研究的3年結果顯示,篩檢型超音波的好處因為較多偽陽性與陰性乳房切片而略減。研究者也發現,進行篩檢型乳房X光檢查加超音波檢查後3年,乳房磁振造影(MRI)診斷率較高(多發現56%的侵犯性乳癌),但是,限制包括偽陽性增加費用、成本較高、病患抗拒該手術。
  
  匹茲堡大學放射科Wendie A. Berg博士表示,這篇發表於4月4日JAMA期刊的研究,是第一篇具體探討乳癌篩檢超音波之臨床意義的重要研究。
  
  美國癌症協會癌症篩檢資深主任Robert A. Smith博士表示,這是篇重要研究,因為它指出了進行乳房造影可以如何改善緻密乳房婦女或先天易患乳癌婦女的檢查;Smith博士未參與該研究。
  
  Berg博士形容緻密乳房組織對癌症預防與發生率而言,可說是「禍不單行」。她表示,緻密乳房婦女發生乳癌的風險是脂肪性乳房婦女的5倍之多,而乳房X光攝影傾向會錯過緻密乳房中的癌症。
  
  這篇試驗在21個機構進行,也確認了使用醫療影像為中度風險婦女進行篩檢的價值。研究中,8成婦女屬於這類,45%有乳癌病史,例如進行過乳房腫瘤切除術和放射線治療、或家族中曾有乳癌或卵巢癌患者;之前的非均質性緻密或極度緻密乳房組織的X光檢查證據是必要的。
  
  研究對象納入時的平均年紀為55歲,不過,只要符合該研究的風險規範,即便年僅25歲者也會納入。
  
  試驗開始時,這些婦女在單一影像機構進行乳房超音波檢查與篩檢型乳房X光攝影,之後在12個月和24個月後再度進行;在612名婦女完成全部3次乳房X光攝影和超音波檢查後,進行乳房MRI。
  
  在這3年間,發現110例乳癌,有89例侵犯性癌症。
  
  乳房X光攝影發現59例癌症(53%),診斷率相當於每1000人有7.9例癌症。
  
  當進行篩檢型超音波時,侵犯性癌症偵測率增加34%,增加診斷率為每1000人有4.3例癌症。
  
  乳房X光攝影和超音波檢查發現的癌症只有8%可以觸診發現,Berg博士指出,這是緻密乳房婦女預期偵測篩檢期間癌症率的一半,低於脂肪性乳房婦女之前報告指出的10%篩檢期間偵測率。
  
  乳房MRI增加了56%癌症偵測率,相當於每1000人增加發現14.7例癌症(95% CI,3.5 - 25.9癌症/1000人;P = .004[與乳房X光攝影加超音波相比])。不過,篩檢型超音波和MRI需要額外的臨床費用,Smith博士稱之為「確實是相當大的差異」。
  
  進行超音波篩檢的婦女有7%(95% CI,6.3% - 7.8%)需要額外檢查,包括5%轉介乳房切片,但只有7.4%的切片獲得陽性的癌症組織學結果。
  
  進行MRI的612人中,乳房X光攝影和超音波檢查後的切片比率為6.2%(95% CI,4.4% - 8.4%),加入MRI後,切片率增加到81/612 (13.2%;95% CI,10.7%- 16.2%)(P < .001),這些手術只有19%獲得陽性癌症診斷。
  
  諸多其他因素使Berg博士等人還不建議將MRI作為中度風險婦女之例行篩檢的一部分,包括MRI費用比超音波貴上許多,及所需的配套設備和受過訓練的專業人員等限制,此外,婦女對乳房MRI的耐受不佳。
  
  在14個地點免費為選定的研究對象提供這些檢查。
  
  她表示,令我們驚訝的是,只有58%的婦女實際上要進行MRI。
  
  Berg博士表示,篩檢型超音波因為本身操作相關的問題受到批評,低給付率和高營運成本使它並不具經濟上的平衡優點,健康照護機構並不被鼓勵提供這項服務。
  
  如果美國癌症協會建議併用乳房X光攝影和超音波篩檢於中度風險婦女,這類問題會被提出,就像2007年、它的指引修改指出篩檢型MRI用於先天乳癌高風險婦女的好處時。
  
  Smith博士表示,ACS下次更新指引時,需要考量中度風險者乳癌篩檢的特定規範。我們一定要檢視這篇研究和其他試驗,以確認資料是否足以提供明確的指引給婦女和轉診的醫師,判斷是否需要不同的篩檢方法。
  
  ACS的乳癌篩檢更新版指引登載於今年初的JAMA,更新的過程一般需要12個月,或許在2012年底會有新版問世。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=6780&x_classno=0&x_chkdelpoint=Y
  

Ultrasound Adds to Mammography's Diagnostic Power for At-Risk Women

By James Brice
Medscape Medical News

April 3, 2012 — Annual screening mammography and breast ultrasound exams detect 34% more invasive breast cancers than mammography alone, according to a new multicenter study involving 2662 women with dense breasts and a moderately elevated risk for breast cancer.

Final results of the 3-year American College of Radiology Imaging Network (ACRIN) 6666 study showed that the benefits of screening ultrasound are tempered by more false-positives and negative breast biopsies.

The researchers also found that breast magnetic resonance imaging (MRI) after 3 years of screening mammography and ultrasound raises the diagnostic yield even higher (56% more invasive breast cancers detected), but at the cost of increased false-positives, higher financial expenses, and patient resistance to the procedure.

The study, which is published in the April 4 issue of JAMA, is the first major scientific inquiry to examine the specific, clinical relevance of breast cancers detected with screening ultrasound, principal investigator Wendie A. Berg, MD, PhD, from the Department of Radiology, University of Pittsburgh, Pennsylvania, said to Medscape Medical News.

The study is important because it addresses how the performance of breast imaging can be improved for women who have dense breasts or are inherently susceptible to breast cancer, Robert A. Smith, PhD, senior director of cancer screening at the American Cancer Society, said in an interview with Medscape Medical News. Dr. Smith was not involved in the study.

Dr. Berg characterized dense breast tissue as a "double whammy" in the context of cancer incidence and prevention. Women with dense breasts are up to 5 times more likely to develop breast cancer than women with fatty breasts, and mammography tends to miss cancers that reside in dense breasts, she said.

The trial, performed at 21 facilities, also confirmed the value of intensified screening using medical imaging for intermediate-risk women. Eight of 10 women in the study fell into that category, with 45% having a personal history of breast cancer, such as past lumpectomy and radiation therapy or a family member who was diagnosed with breast or ovarian cancer. Evidence from previous mammography of heterogeneously dense or extremely dense tissue was required.

The average age of participants at enrollment was 55 years, although women as young as 25 years were eligible when they met the study's at-risk criteria.

The women received breast ultrasound exams and screening mammograms in a single imaging session at the start of the trial, and then again 12 and 24 months later. Breast MRI was offered at the end of the series to 612 women who completed all 3 mammography and ultrasound screenings.

Improved Cancer Detection

Over the course of 3 years, 110 breast cancers were detected, with 89 cases involving invasive cancers.

Fifty-nine cancers (53%) were detected by mammography. Its diagnostic yield was the equivalent of 7.9 cancers per 1000 population.

The detection of invasive cancers increased 34% when screening ultrasound was performed. Its additional yield averaged 4.3 cancers per 1000 patients.

Only 8% of the cancers detected with mammography and ultrasound were palpable. This was half the expected rate of detected interval cancers for dense-breasted women, and lower than the 10% interval detection rate reported previously for women with fatty breasts, Dr. Berg noted.

Breast MRI raised cancer detection rate 56% and increased the yield by 14.7 cancers per 1000 (95% CI, 3.5 - 25.9 cancers per 1000; P = .004 vs mammogram plus ultrasound).

Clinical Costs of Higher Sensitivity

However, screening ultrasound and MRI involved added clinical costs that Dr. Smith characterized as "really quite significant."

Seven percent of women (95% CI, 6.3% - 7.8%) who underwent ultrasound screening required extra testing, including 5% referred for breast biopsies. Only 7.4% of the biopsies yielded a positive histological finding of cancer.

Of the 612 MRI participants, the rate of biopsy after mammography plus ultrasound was 6.2%; (95% CI, 4.4% - 8.4%). The rate of biopsy increased to 81 of 612 (13.2%; 95% CI, 10.7% - 16.2%) with the addition of MRI (P < .001). Only 19% of those procedures produced a positive cancer diagnosis.

Several additional factors led Dr. Berg and colleagues to recommend against MRI as a routine part of screening for intermediate-risk women, including that MRI is several times more expensive than ultrasound and access is limited because of required accessory equipment and specially trained personnel. In addition, breast MRI is not well-tolerated by women, Dr. Berg said.

Selected trial participants were offered the procedures for free at the 14 sites equipped to perform the procedures.

"We were surprised that only 58% of the women actually wanted to have the MRI," she said.

Screening ultrasound was beset by its own set of practice-related problems, Dr. Berg said. Low reimbursement rates and high operational costs make it no better than a break-even financial proposition, and healthcare facilities are discouraged from offering the service, she said.

Such problems could be addressed if the American Cancer Society recommends the combined mammography–ultrasound screening protocol for intermediate-risk women, as it did in 2007 when its guidelines were modified to acknowledge the benefits of screening MRI for high-risk women who are genetically susceptible to breast cancer.

A specific provision addressing breast cancer screening for the intermediate-risk group will be considered the next time ACS updates its guidelines, Dr. Smith told Medscape Medical News.

"We would certainly examine this study and others to determine if the data were sufficiently strong to provide clear guidance to women and referring physicians about whether different approaches to screening are needed," he said.

An ACS update on breast cancer screening guidelines was published in JAMA earlier this year. The update process, which typically takes about 12 months, will begin in late 2012, he said.

The study was funded by the Avon Foundation and grants from the National Cancer Institute. Dr. Berg has served as a consultant to Naviscan Inc and SuperSonic Imagine, has received research support from Naviscan, has prepared educational materials for Gamma Medica, has a research grant from Hologic Inc, and is on the medical advisory board of Philips Medical Systems. Dr. Smith has disclosed no relevant financial relationships. Full disclosure information for the authors is available on the journal's Web site.

JAMA. 2012;307:1394-1404.

    
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