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Edited comments by Dr Krag
Rationale for axillary lymph node dissection (ALND)
The rationale for performing ALND is threefold: regional control, staging and prognosis, and the possibility of improving survival. Most people regard staging as the primary value derived from ALND; but in fact, we also use it because of presumed therapeutic benefit. Data from a variety of sources document the accuracy of SLNB for staging the axilla. If staging were our primary concern, then we could simply utilize SLNB, but regional control and survival must be considered.
We don't have any data on long-term regional control rates for SLNB, but we know that ALND achieves nearly 100 percent control in the axillary region, and radiation has a similar control rate. Abandoning these procedures, which we know work very well therapeutically, would be a big step because the mortality associated with regional recurrence is approximately 50 percent.
It's somewhat heretical to say this, but there may be a survival benefit from controlling the axilla. I make this point because not many studies have excluded ALND. In addition, in the few NSABP studies in which ALND was not performed, hundreds - not thousands - of patients were randomized. Although the data in these studies demonstrated no survival differences between ALND and SLNB, these trials did not have the statistical power to detect survival differences of five percent or less.
I do not believe we have enough data to justify SLNB in a nonprotocol setting, and I've personally never performed SLNB in a breast cancer patient outside of a clinical trial.
Methodologies in performing SLNB
SLNB is not a quick "get-in and get-out" surgery. Occasionally, the node is easy to find, and you're done in about 10 minutes. However, in about one-third of cases, the node is not obvious, and the procedure is time-consuming - often more so than ALND. SLNB is a delicate surgery, and I believe that lack of patience is one of the most common mistakes made while performing it.
In the United States, there are limited methods to perform SLNB. There are dye-based methods, including blue dye and isosulfan blue (LymphazurinTM), and radioactive tracers - typically, technetium sulfur colloid. The other important methodological factor is the location of the injection. The injection can be deep - either into or around the tumor - or superficial into the skin that overlies the tumor or the skin adjacent to the areola complex.
Each method has advantages and disadvantages. If you want to capture the lymphatic ducts leading from a tumor, it is logical to inject the dye or tracer around the tumor; however, data show that injections into the skin or an alternate location also produce good results.
Confirmatory ALNDs performed on large numbers of patients - collectively, thousands of patients using different injection locations - have measured both SLNB success rates and whether the correct node was located. We've collated this data and found high success rates - from 90 percent to 98 percent - in all categories. The rates of finding pathologically positive nodes with any given technique differ. The positivity rate is about 35 percent when the injection is intradermal over the tumor or intra- or peritumoral, which is consistent with our expectations. However, in the subareolar category, the rate is approximately 27 percent. I hope that this nearly 10 percent difference reflects patient selection and a limited data set, but the results are from more than 500 patients. At the very least, questions have been raised regarding use of the technique in this location.
SLNB with neoadjuvant systemic therapy
Data suggests SLNB works quite well in the neoadjuvant setting. There is also information that suggests it could be used reasonably in patients with multiple tumors throughout the breast. I also believe that it would not be harmful to perform SLNB in conjunction with ALND in patients with locally advanced disease because it can guide the pathologist to nodes more likely to contain cancer and may assist in detecting additional axillary nodes that would be important to resect.
Replacement study for NSABP-B-32
We're working on a correlative pathology study that is conceptually linked to B-32 but is not really a sentinel node study. We're attempting to incorporate the most current technologies in a prospective manner to evaluate bone marrow aspirates and peripheral blood samples. We also want to perform genomic studies on the primary tumor. To minimize patient discomfort, we would perform the bone marrow aspiration and collect peripheral blood procedures at the time of surgery.
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