The Sentinel Node in Breast Cancer -- A Multicenter Validation Study
Reviewers: Kenneth Blank, MD and John Han-Chih Chang, MD
Source: The New England Journal of Medicine -- October 1, 1998 -- Volume 339, Number 14
The treatment of invasive breast cancer always includes dissection of the axilla (the area of tissue under the armpit) to determine if lymph nodes in this area have been invaded by cancer. An axillary dissection guides therapy in the post-operative period: the number of lymph nodes positive, if any, may determine what type and how long chemotherapy is dosed. In addition, most doctors believe that if there are no lymph nodes with cancer then radiation to the axilla can be avoided. However, an axillary dissection is not without morbidity, the most concerning of which is arm edema (swelling) which occurs to varying degrees in about 10% of women.
Sentinel node biopsy is an investigational technique to determine the status of the axillary lymph nodes without performing a full axillary dissection. Using radioisotpes or blue dye surgeons identify and remove just one or two lymph nodes (the sentinel nodes) for pathologic evaluation. While this procedure avoids the morbidity of a full axillary dissection, is relies on the theory that cancer spreads in an orderly progression from the breast tissue into the sentinel node then into other nodes in the axilla. However, it remains to be proven whether the status of the sentinel node is indicative of other lymph nodes in the axilla. Towards this end several papers have reported on cohorts of women who undergo sentinel lymph node biopsy followed immediately by an axillary dissection, which allows investigators to determine if the pathologic status of the sentinel lymph node is indicative of rest of the lymph nodes.
Materials and Methods
A multicenter study performed at American institutions was reported in the October 1, 1998 New England Journal of Medicine. Four hundreds and forty three women were enrolled on this study between May 1995 and September 1997. A radioisotope was injected into the tumor cavity and using a gamma probe hot spots were identified in the axilla. Lymph nodes in these hot spots were removed and labeled the sentinel lymph node(s). All women then underwent an axillary dissection and the pathologic status of the sentinel node was compared with the rest of the axilla.
In thirteen of the 443 patients the sentinel node was negative for cancer but other lymph nodes in the axilla were positive. It is this scenario which is most concerning to physicians and patients because, if sentinel node biopsy gains acceptance in place of the axillary dissection, these women would be counseled under the false assumption that there was no cancer in the axillary lymph nodes.
Discussion and Conclusion
Sentinel lymph node biopsy remains investigational but will surely have a place in the treatment of breast cancer. It is critical for patients to discuss with their doctors the risks and benefits of sentinel node biopsy versus a complete axillary dissection.