In a study presented today (Wednesday) at the European Cancer Conference (ECCO 14) in Barcelona, scientists found that the less invasive technique produced a false positive rate of only one percent, so that 99 percent of patients with healthy lymph nodes were correctly classified.
The study, the largest of its kind to date, tested the accuracy of the new technique in 590 patients with recently diagnosed melanoma who underwent an ultrasound of the lymph node region near their tumours before having the sentinel lymph node cut out for examination. If the ultrasound confirmed cancer or looked suspicious, patients also underwent the fine needle aspiration biopsy before the sentinel node surgery. Survival was tracked for an average of 28 months.
"The fine needle aspiration detected tumour cells in the lymph node of half of the patients who were later shown to have node-positive disease through the surgical sentinel node biopsy procedure. In nearly all the cases that it missed, the tumour deposit in the sentinel node was very small and those patients seem to have an excellent prognosis - their survival seems similar to that seen in patients with no spread to the lymph nodes," said the study's leader, Dr Christiane Voit, a dermatologist and head of the diagnostic unit at the Skin Cancer Center at Charité - Universitätsmedizin Berlin, the Medical University of Berlin, Germany. "This study shows that the technique is highly accurate and we are recommending that it should now be performed routinely before automatically performing sentinel lymph node biopsies, as a way to reduce the need for unnecessary sentinel node operations."
Whether cancer has spread to the lymph nodes is the most important factor influencing the prognosis and treatment plan for patients with melanoma. Lymph node surgery for tumour staging has become more refined and less debilitating over the last decade. Traditional operations involve the removal of all lymph tissue from the area that drains the site of the tumour, but in some cancers, including melanoma, doctors now more often cut out only one or two key nodes, called sentinel nodes. If the sentinel node is free of cancer, patients don't need to have more extensive lymph node removal.
However, only 20 percent of patients who have their sentinel lymph nodes excised have cancer that has spread there, so the operation, which can still be accompanied by side effects such as chronic swelling and seroma, is unnecessary for 80 percent of patients.
"Sentinel node biopsy (the excision of only one node instead of all regional lymph nodes) is already an improvement over complete removal of all the lymph nodes in the axilla, groin or neck, but we still need a better way to identify which patients need their sentinel lymph nodes cut out and which don't, so that all those patients who are subjected to unnecessary surgery can avoid it. Ultrasound-guided fine needle aspiration does look better," said Voit, adding that the procedure does not cause the side effects seen in sentinel node biopsy. The sometimes-claimed danger of spreading of tumour cells along the needle tract was not evident in this study, nor in previous studies the group has conducted using the method, Voit added.
The technique, called ultrasound-guided fine needle aspiration cytology, or US-FNAC, has been reported to be useful in replacing the need for a sentinel node biopsy in breast cancer, but has not yet been accepted as a valuable option to avoid surgical sentinel node biopsy in melanoma.