HOLLYWOOD, Florida (EGMN) –A cautious footnote about the use of magnetic resonance imaging to stage breast cancer or to gauge response to breast cancer therapy was added to guidelines from an alliance of 21 leading cancer centers.

“The value of MRI is uncertain, practice varies, and the potential downsides are real,” Dr. Stephen B. Edge said at the annual conference of the National Comprehensive Cancer Network (NCCN). “This is a rapidly evolving area in practice. This is an area where there is no consensus.”

To guide clinicians on the utility of MRI in breast cancer, NCCN added six new recommendations to the Principles of Dedicated Breast MRI Testing section of the guidelines. (Unless noted, all are grade 2A recommendations, reflecting uniform consensus from NCCN panel members.)

This section said that MRI may be useful to stage the extent of cancer or to detect multifocal or multicentric disease in the ipsilateral breast, or to screen the contralateral breast at time of diagnosis (a category 2B recommendation, which has the same level of evidence as a 2A recommendation, but with nonuniform NCCN consensus).

“The impact of identification of contralateral cancers is unclear,” Dr. Edge said. MRI leads to frequent biopsies, 75%-80% of which are benign, he added. For example, in an MRI screening study of 969 women with a normal mammogram, 121 had a biopsy-based on MRI lesion detection, and 30 (3%) of the 969 women had a diagnosis of contralateral cancer (N. Engl. J. Med. 2007;356:1295-303).

MRI may also be useful before and after neoadjuvant therapy to define the extent of disease or response to therapy. In addition, “MRI can help assess candidacy for surgery after adjuvant therapy,” said Dr. Edge, chair of the department of breast surgery and medical director of the Breast Center at Roswell Park Cancer Institute in Buffalo, New York.

However, MRI findings may underestimate residual disease, he said. In one study, “unfortunately, half of women cleared by MRI still had residual tumor at time of surgery” (Br. J. Cancer. 2004;90:1349-60). “So, complete clearance on MRI does not mean complete clinical clearance. There is clearly a need for prospective data in this field.”

MRI may be helpful to detect additional disease in women with a dense breast on mammography, the guidelines state (although available data do not indicate any difference in MRI detection by breast density or disease type).

In addition, MRI may be useful to identify primary cancer in women with axillary node adenocarcinoma or with Paget’s disease of the nipple when primary breast disease is not identified on mammography, ultrasound, or physical exam.

Also, because of a high rate of false-positive findings, the panel concluded that surgical decisions should not be based solely on MRI findings. For example, a multicenter study of 426 women with a suspicious mammogram and proven cancer revealed a 24% incidental lesion false-positive rate with MRI, compared with 10% false-positive rate with mammography (J. Surg. Oncol. 2005;92:32-8). “But MRI also detected some additional lesions,” Dr. Edge said.

An unanswered question is whether MRI affects long-term breast cancer outcome and survival, Dr. Edge said. “The only available evidence—retrospective data—shows no impact of MRI on local recurrence or survival.”

Another updated NCCN guideline, this one on breast cancer screening and diagnosis, states that physicians can consider MRI as an adjunct to screening high-risk women in addition to annual mammography and breast exam. New definitions of high-risk patients include women aged 25 years and older with a history of thoracic radiotherapy, and those with a lifetime risk of breast cancer exceeding 20%. MRI is not recommended for screening average-risk women.

The NCCN guidelines panel also included MRI expertise recommendations. For example, an expert breast-imaging team should perform and interpret breast MRI examinations, working in concert with a multidisciplinary treatment team. In addition, breast MRI should be done by a radiologist with expertise in breast imaging using a dedicated coil. Also, an imaging center should have the ability to perform MRI-guided needle sampling and/or wire localization of relevant findings.

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佛罗里达州好莱坞(EGMN)——由21家顶尖癌症中心组成的联盟——NCCN，在其指南中谨慎地将关于如何使用磁共振成像技术（MRI）对乳腺癌分期或评估乳腺癌治疗疗效作为脚注加入其中。

“MRI价值是不确定的，操作各有不同，潜在的缺点是真实存在的。” Stephen B. Edge博士在美国国家综合癌症网络(NCCN) 年度会议上说道。“这是临床实践中迅速发展的领域。这也是一个没有形成共识的领域。”

为了指导MRI在乳腺癌中的应用，NCCN在指南中“MRI在乳腺癌的检查原则”这一节增加了6个新的建议。(除非特别注明，所有建议均为2A级，反映了NCCN小组成员统一的共识。)

本节写道，MRI检查可能对肿瘤分期、同侧乳房多滤泡或多中心病变探查、对侧乳房诊断性筛查有益（第2B类建议，与2A级建议属同一水平，但非统一性NCCN共识）。

“目前还不清楚MRI对另一侧乳房肿瘤诊断的影响。”Edge博士说。根据MRI检查结果进行的活检，75%~80%是良性的，他补充说。例如，利用MRI对 X光报告正常的969例女性乳房进行检查，其中121例根据MRI检查结果做了活检，969例女性当中有30例(3%)诊断出对侧肿瘤(N. Engl. J. Med. 2007;356:1295-303)。

MRI可用来明确新辅助治疗前后疾病的范围或治疗疗效。此外，“MRI可帮助评估辅助治疗后的手术选择。”纽约州布法罗罗兹韦尔公园癌症研究所乳腺中心乳腺外科主任和医务主任Edge博士说。

然而， MRI检查也可能会漏诊残余病变，他说。在一项研究中，“不幸的是，手术中发现经MRI排除的乳腺癌患者仍有一半存在残余肿瘤灶。”(Br. J. Cancer. 2004;90:1349-60)“所以，MRI检查排除病情并不意味着临床排除。但很显然，在该领域预期资料是需要的。”

MRI可能有助于发现钼靶X线示致密征的女性乳腺癌患者的其他病变，该指南指出。(尽管现有数据不能说明MRI在检查乳房密度或疾病类型有任何区别)。

此外，当体检、超声波或钼靶X线检查不出原发肿瘤时，MRI检查可能有助于确定腋窝淋巴结腺癌或乳头Paget病女性患者的肿瘤原发灶。

该小组总结说，由于结果假阳性率高，是否手术不应仅仅根据MRI表现。比如在一个包括426例乳房成像检查疑似乳腺癌患者的多中心研究中，经活检证实，MRI检查有24% 的假阳性率，钼靶X线检查假阳性率则为10%。(J. Surg. Oncol. 2005;92:32-8)“但MRI可检查出一些其他的病变。” Edge博士说。

 “一个没有得到回答的问题是，MRI是否会影响乳腺癌患者的长期预后和生存期，”Edge博士说。“目前仅有的证据(一份回溯性数据)表明MRI对局部复发或生存期没有影响。”

另一个关于乳腺癌筛查和诊断的NCCN最新指南指出，医生可以考虑将MRI作为除每年的钼靶X线检查和乳房检查之外筛查乳腺癌高危妇女的辅助手段。新的对乳腺癌高危人群的定义是指25岁以上有胸部放疗史的女性患者，以及终身乳腺癌罹患风险超过20%的人群。不建议对平均罹患风险水平的女性进行MRI筛查。

该NCCN指南还包括MRI专家建议。例如，乳腺影像专家小组应履行乳腺MRI检查的解释工作，并与多学科的治疗小组协同工作。此外，乳腺MRI检查应由专长于乳腺显像的放射学专家进行，并使用专用线圈。此外，影像中心还应具备MRI引导细针穿刺取样和或相关结果的线圈定位技术。 

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