Tumor Burden in Sentinel Node May Help Stratify High- and Low-risk Vulvar Cancer Patients
Tumor burden in the sentinel node of early-stage vulvar cancer patients appears to be an important prognostic factor. Patients with sentinel-node metastasis larger than 2mm may have a worse prognosis. These findings were recently published in the journal The Lancet Oncology.
Vulvar cancer is a rare type of cancer that affects a female’s outer genitalia. The majority of vulvar cancers are squamous cell carcinomas.
In order to evaluate whether vulvar cancer has spread, surgeons typically perform a sentinel lymph node biopsy. This procedure is a less-invasive technique than a pelvic lymph node dissection (removal of lymph nodes) and allows the surgeon to remove only one to three nodes, called the sentinel nodes. The sentinel node is the first node that drains a particular area, such as the pelvis. In a sentinel node biopsy, the surgeon injects a dye into the affected area to identify which node is the first to be marked by the dye and then removes that node. If the sentinel lymph node is free of cancer, then it is unlikely any of the other lymph nodes located “downstream” have cancer and they are not removed. If, however, the sentinel node does contain cancer, surgeons will usually proceed with a full pelvic lymph node dissection.
To determine whether or not the sentinel node contains cancer, a pathologist may use several techniques that involve either routine assessment with a microscope or more advanced procedures such as immunohistochemistry techniques. These “ultrastaging” techniques allow pathologists to detect smaller and smaller micrometastases down to isolated tumor cells. As sentinel node biopsy has become standard in many cancers, research is ongoing to determine how these techniques can be used to stratify patients into high-, intermediate-, and low-risk groups in order to individualize care and determine appropriate treatment.
In this prospective observational study, 403 patients with early-stage squamous cell vulvar cancer underwent surgical removal of their cancer as well as a sentinel lymph node biopsy. In 135 patients, metastatic disease was detected in the sentinel node(s) by routine pathology. Patients who had cancer in their sentinel lymph node underwent a pelvic lymph node dissection on either one or both sides of their pelvis. The size of sentinel-node metastases appeared to be associated with disease-specific survival. Patients with isolated tumor cells in their sentinel node had a 97% five-year disease-specific survival compared with 88% for those with sentinel-node metastases 2 mm or smaller and approximately 70% for those with metastases larger than 2 mm. Although survival was better for patients with smaller disease in their sentinel node, these researchers “did not find a cut-off size for sentinel-node metastasis below which the risk of additional groin metastases becomes negligible.”
The researchers concluded that sentinel-node metastasis of any size requires further treatment and that patients with sentinel-node metastasis larger than 2 mm appear to have a worse prognosis.
 Oonk MH, van Hemel BM, Hollema H, et al. Size of sentinel-node metastasis and chances of non-sentinel-node involvement and survival in early stage vulvar cancer: results from GROINSS-V, a multicentre observational study. The Lancet Oncology [early online publication]. May 26, 2010.
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