The role of axillary dissection in the management of operable breast cancer is controversial. Lymph node status has been used to determine the prognosis of patients with breast cancer. Axillary node dissection has also been thought to control axillary disease and may improve the overall rate of survival because the removal of microscopic nodal metastases may be curative in certain patients. Recently, the overall rate of survival has been thought to depend more on distant metastases and is probably not affected by axillary dissection in most patients. Lymphatic mapping and sentinel lymph node biopsy are new techniques that provide accurate staging information while causing less morbidity than axillary dissection. Bass and associates evaluated the effectiveness of lymphatic mapping and sentinel lymph node biopsy in the surgical treatment of patients with breast cancer.
Lymphatic mapping with lymphoscintigraphy has been used to identify appropriate nodal basins to which melanoma may have spread. Singular lymph nodes can be identified in the various basins by injecting technetium 99 compounds into the subdermal lymphatic plexus. A sentinel node, which is the first lymph node in the pathway to the regional basin, can be identified by injecting a special blue dye. The results from studies of the sentinel node to detect melanoma cells are now being transferred to the evaluation of breast cancer lymph node metastases. Breast cancer differs from melanoma in that the slower growth rate delays the development of clinically detectable, recurrent nodal metastases. Adjuvant therapies may further extend these delays in node-negative patients.
Sentinel lymph node mapping in patients with breast carcinoma lowers surgical morbidity, is more cost effective and may be superior because it allows for close examination of the lymph nodes that are at greatest risk. Methods of identifying the appropriate lymph node include: (1) the blue dye technique, in which blue dye is injected into the parenchymal breast tissue around the tumor and picked up by the lymphatic vessels, staining the sentinel lymph node; (2) the radiocolloid technique, in which radiocolloid with saline is injected around the tumor or biopsy site and a gamma detection probe is used intraoperatively to localize the sentinel lymph node; and (3) a combination technique, in which blue dye and radiocolloid are injected around the tumor or biopsy site.
The authors evaluated 700 patients with breast cancer in whom the combination technique was applied. Sentinel lymph nodes were successfully identified in 665 patients (95 percent). In each patient, an average of 2.03 sentinel lymph nodes were removed. A learning curve was identified, demonstrating that 100 operations were required to achieve a 95 percent success rate in identifying an axillary sentinel lymph node.
The authors conclude that lymphatic mapping eliminates the need for extensive axillary dissection in a majority of patients, significantly reducing surgical morbidity. Providing the pathologist with one or two sentinel lymph nodes, instead of multiple nodes, allows for a more focused evaluation with better detection of micrometastases. The authors feel that the impact of this new technique on the rate of breast cancer survival requires further study.
In a related article in the same issue, Hsueh and associates echo the value of sentinel node biopsy in the treatment of breast cancer and its ability to spare node-negative patients the morbidity of axillary dissection. The best technique and the surgeons' learning curve have yet to be determined.
editor's note: The role of axillary dissection in the treatment of invasive breast cancer is being re-evaluated. Although node metastases aid in prognosis determination, the use of adjuvant systemic therapy makes this information less important for therapeutic decisions. The use of sentinel lymphadenectomy to identify micrometastases is becoming more popular, even though regional nodal dissection is recognized as useful in controlling nodal disease. One of the supporting arguments for sentinel node surgery is that full axillary node dissection causes significant complications. Another option is level I and level II axillary node dissection with preservation of the pectoralis minor; the incidence of level III micrometastases without abnormalities at the two lower levels is rare. Roses and associates studied a series of patients who received level I and II node dissections (Roses DF, et al. Complications of level I and II axillary dissection in the treatment of carcinoma of the breast. Ann Surg August 1999;230:194–201). They noted minimal lymphedema, no range-of-motion difficulties, no prolonged pain, minimal numbness or parasthesias, and no recurrent disease in the axilla. They conclude that the question of whether sentinel node lymphadenectomy will eliminate elective axillary dissection should not be determined by the difference in morbidity rates. Because many sentinel node biopsies are followed by complete axillary dissections, the usefulness of the ability to more exhaustively evaluate the sentinel node for micrometastases may require further study.—r.s.