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When sentinel lymph nodes (SLNs) and bone marrow are stained using immunohistochemical (IHC) methods, breast cancer metastases can be seen that are not visible with routine clinical or pathological examination. Previously, it had been thought that when occult (ie, microscopic) cancer cells are found in the SLN closest to the tumor, removing the sentinel node and the surrounding lymph nodes would improve survival rates. However, a study released yesterday in the Journal of the American Medical Association authored by the American College of Surgeons Oncology Group (ACOSOG) found that removing the SLN and all surrounding lymph nodes has no effect on overall survival compared with those patients who had only the SLN removed.
ACOSOG initiated the Z0010 trial in May 1999. The trial ran until May 2003 at 126 different sites and all patients were then followed until April 2010. A total of 5210 women had clinical T1 to T2N0M0 invasive cancer of the breast and underwent breast-conserving surgery and SLN dissection. Of the 5119 SLN specimens, 3904 (76.3%) tested negative for tumors by IHC staining. The 3326 SLN specimens that were IHC stained tested positive for tumors in 349 (10.5%) of the cases. Of 3413 bone marrow specimens that were IHC stained, 349 (10.5%) were positive for tumors. (Occult bone marrow metastasis is considered rare and is associated with decreased survival.)
At a midpoint follow-up of 6.3 years, the authors reported that 435 of the women died and 376 experienced disease recurrence. For those whose SLN biopsies tested positive for cancer cells as a result of IHC staining, the 5-year survival rate was 95.1%; those whose SLN biopsies tested negative for node involvement had a 5-year survival rate of 95.7%.
Armando E. Giuliano, MD, lead investigator of the study, has published previously on the mistaken belief that removing the SLN closest to the tumor and all surrounding lymph nodes improves survival rates. He said the ACOSOG study proves that even with microscopic SLN metastases, survival outcomes are not affected. He noted that the results show that it is not necessary to have all lymph nodes removed, a process that can cause chronic, painful lymphedema in patients.
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