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Ultrasonography not a reliable replacement for sentinel lymph node biopsy

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – For patients with primary cutaneous melanoma, targeted high-resolution ultrasound should not be used as a substitute for excisional sentinal lymph node biopsy, new research indicates.

However, “ultrasound is of value in preoperative sentinel lymph node assessment and postoperative monitoring,” Dr. John F. Thomson at the Melanoma Institute Australia in N. Sydney, New South Wales, and co-investigators report in the September 28th online issue of the Journal of Clinical Oncology.

The team identified and removed sentinel lymph node biopsies from 871 lymph node fields in 716 patients. Histologically positive nodes were identified in 144 lymph node fields (16.5%) in 125 patients (17.5%).

Ultrasound was true positive for metastases in 28 patients and 35 node fields. The sensitivity of ultrasound for all lymph node fields was 24.3%, and specificity was 96.8%, the authors report. Positive predictive value was 60.3%, and negative predictive value was 86.6%.

“The great number of false negative results indicates that ultrasound cannot be used reliably as an alternative to sentinel lymph node biopsy,” Dr. Thomson’s team maintains.

On the other hand, sensitivity improved with greater Breslow thickness of melanoma. The median histologic cross-sectional area of the sentinal lymph node metastatic deposits was 0.39 mm2 (12.75 mm2 for ultrasound true-positive results and 0.22 mm2 for false-negative results). Ultrasound-detected deposits were more likely to be spherical in cross-section than the typical ovoid shape of lymph nodes.

“Ultrasound also has a role in closely monitoring patients who elect not to have a sentinel lymph node biopsy or who have a contraindication to surgery and who undergo regular imaging of their identified sentinel lymph node instead,” the authors conclude.

J Clin Oncol 2009.