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Is the ”10% Rule” Equally Valid for All Subsets of Sentinel-Node-Positive Breast Cancer Patients?
expensive noninvasive imaging and high false-positive biopsy rates. Mammary ductoscopy, which can help surgeons find and direct earlier therapy and utilizes relatively
inexpensive equipment and personnel already engaged in the fight against breast cancer, could become a welcome and much needed, more practical alternative in regions where
the medical infrastructure is less rich in technologic resources. W. C. Dooley, MD
SENTINEL NODE BIOPSY Is the ''10% Rule'' Equally Valid for All Subsets of SentinelNode-Positive Breast Cancer Patients? Chung A, Yu J, Stempel M, et al (Memorial Sloan-Kettering Cancer Ctr, NY) Ann Surg Oncol 15:2728-2733, 2008
Background.—In breast cancer, a combination of radioisotope and blue dye mapping maximizes the success and accuracy of sentinel node (SLN) biopsy. When multiple radioactive nodes are present, there is no single definition of isotope success, but the popular ‘‘10% rule’’ dictates removal of all SLN with counts >10% of the most radioactive node. Here we determine how frequently a positive SLN would be missed by the 10% rule. Methods.—Between 9/96 and 12/04, we performed 6,369 successful SLN biopsies using 99mTc sulfur colloid and isosulfan blue dye, removing as SLN all radioactive and/ or blue nodes, and taking counts from each node ex vivo. Standard processing of all SLNs with a benign frozen section included hematoxylin and eosin (H&E) staining, serial sectioning, and immunohistochemistry (IHC).
Results.—33% of patients (2,130/ 6,369) had positive SLNs. Of these patients, 1,387/2,130 (65%) had >1 SLN identified. The most radioactive SLN was benign in 29% (398/1,387), and 107/1,387 (8%) had a positive SLN that was neither blue nor the hottest. From this group 1.7% (24/ 1387) of patients had positive SLN with counts <10% radioactive counts of the hottest node. The 10% rule captured 98.3% of positive nodes in patients with multiple SLNs. No patient characteristics were predictive of failure of the 10% rule. Conclusion.—With combined isotope and blue dye mapping, the 10% rule is a robust guideline and fails to identify only 1.7% (24/1387) of all SLN-positive patients with multiple SLNs. This guideline appears to be equally valid for all subsets of patients. SLN biopsy has become widely accepted as an appropriate minimally invasive means of staging the axilla in patients with breast cancer. In this study from Memorial Sloan-Kettering Cancer Center, the authors evaluated what has come to be known as the ‘‘10% rule’’: an SLN is defined not only as the hottest node, any blue
node, or any node at the end of a blue lymphatic channel, but also as any node that has radioactive counts greater than 10% of the hottest node. The authors found that by using these 4 criteria, 98.3% of node-positive patients were identified. Although it is wonderful that the authors concluded that this is a robust guideline (since most surgeons have adopted these criteria), their study brings up some other important issues, which give us some pause. For example, of the 107 patients who had a positive SLN that was not the hottest node or a blue node, 24 (22%) had a positive SLN that had counts less than 10% of the hottest node; and of the 19 patients in this cohort who underwent axillary dissection, 3 (16%) had positive nonSLNs. It is important to keep in mind that beyond the nodes that meet these criteria, nodes that are palpably suspicious should also be removed as they may not be hot or blue because the afferent lymphatics may be occluded with tumor. The criteria we have are good guidelines, but even with these, SLN biopsy is not infallible. A. B. Chagpar, MD, MSc, MPH
Breast Diseases: A Year BookÒ Quarterly Vol 20 No 1 2009
67
inexpensive equipment and personnel already engaged in the fight against breast cancer, could become a welcome and much needed, more practical alternative in regions where
the medical infrastructure is less rich in technologic resources. W. C. Dooley, MD
SENTINEL NODE BIOPSY Is the ''10% Rule'' Equally Valid for All Subsets of SentinelNode-Positive Breast Cancer Patients? Chung A, Yu J, Stempel M, et al (Memorial Sloan-Kettering Cancer Ctr, NY) Ann Surg Oncol 15:2728-2733, 2008
Background.—In breast cancer, a combination of radioisotope and blue dye mapping maximizes the success and accuracy of sentinel node (SLN) biopsy. When multiple radioactive nodes are present, there is no single definition of isotope success, but the popular ‘‘10% rule’’ dictates removal of all SLN with counts >10% of the most radioactive node. Here we determine how frequently a positive SLN would be missed by the 10% rule. Methods.—Between 9/96 and 12/04, we performed 6,369 successful SLN biopsies using 99mTc sulfur colloid and isosulfan blue dye, removing as SLN all radioactive and/ or blue nodes, and taking counts from each node ex vivo. Standard processing of all SLNs with a benign frozen section included hematoxylin and eosin (H&E) staining, serial sectioning, and immunohistochemistry (IHC).
Results.—33% of patients (2,130/ 6,369) had positive SLNs. Of these patients, 1,387/2,130 (65%) had >1 SLN identified. The most radioactive SLN was benign in 29% (398/1,387), and 107/1,387 (8%) had a positive SLN that was neither blue nor the hottest. From this group 1.7% (24/ 1387) of patients had positive SLN with counts <10% radioactive counts of the hottest node. The 10% rule captured 98.3% of positive nodes in patients with multiple SLNs. No patient characteristics were predictive of failure of the 10% rule. Conclusion.—With combined isotope and blue dye mapping, the 10% rule is a robust guideline and fails to identify only 1.7% (24/1387) of all SLN-positive patients with multiple SLNs. This guideline appears to be equally valid for all subsets of patients. SLN biopsy has become widely accepted as an appropriate minimally invasive means of staging the axilla in patients with breast cancer. In this study from Memorial Sloan-Kettering Cancer Center, the authors evaluated what has come to be known as the ‘‘10% rule’’: an SLN is defined not only as the hottest node, any blue
node, or any node at the end of a blue lymphatic channel, but also as any node that has radioactive counts greater than 10% of the hottest node. The authors found that by using these 4 criteria, 98.3% of node-positive patients were identified. Although it is wonderful that the authors concluded that this is a robust guideline (since most surgeons have adopted these criteria), their study brings up some other important issues, which give us some pause. For example, of the 107 patients who had a positive SLN that was not the hottest node or a blue node, 24 (22%) had a positive SLN that had counts less than 10% of the hottest node; and of the 19 patients in this cohort who underwent axillary dissection, 3 (16%) had positive nonSLNs. It is important to keep in mind that beyond the nodes that meet these criteria, nodes that are palpably suspicious should also be removed as they may not be hot or blue because the afferent lymphatics may be occluded with tumor. The criteria we have are good guidelines, but even with these, SLN biopsy is not infallible. A. B. Chagpar, MD, MSc, MPH
Breast Diseases: A Year BookÒ Quarterly Vol 20 No 1 2009
67