By Will Boggs MD
NEW YORK (Reuters Health) - Preoperative PET/CT staging in sentinel lymph node (SLN)-positive cutaneous malignant melanoma has a high false-positive rate and does not meaningfully alter clinical management, researchers report.
The National Comprehensive Cancer Network (NCCN) recommends staging by PET/CT prior to lymph node dissection, but the category 2B recommendation lacks high-level supporting evidence.
Dr. Benjamin Y. Scheier and colleagues from the University of Michigan in Ann Arbor undertook a retrospective evaluation of 78 patients with melanoma, clinically silent regional lymph nodes, and positive SLN mapping to assess the value of PET/CT in detecting occult metastases.
Of the 46 patients who underwent preoperative PET/CT, 15 (33%) had intense uptake distant from the primary tumor and local lymph node basin. Nine of these had abnormalities biopsied prior to lymph node dissection, and three yielded metastatic melanoma, for a false-positive rate of 67% in identifying distant metastases.
Only three (7%) of the patients staged with PET/CT had PET/CT findings that ultimately identified metastatic melanoma and precluded lymph node dissection, the researchers report in JAMA Oncology, online September 24.
"We found that PET/CT has a high false-positive rate and a minimal effect on patient management in this setting, and is best reserved in its established role evaluating treatment response and recurrence," the team notes.
"These data also suggest that a significant majority of asymptomatic patients with newly discovered microscopic SLN-positive melanoma do not have synchronous metastases detectable by PET/CT," they add. "Our review also identified the potential for treatment delays, increased exposure to risk from additional procedures, and increased health care resource usage that patients incur following detection of asymptomatic abnormalities by preoperative PET/CT."
They conclude, "We recommend that PET/CT staging be reevaluated as a category 2B recommendation by the NCCN and its use further evaluated prospectively in a clinical trial."
Pathologist Dr. Robin T. Vollmer from Duke University and Durham VA Medical Centers in North Carolina has published widely on malignant melanoma. He told Reuters Health by email, "Given that the PET/CT was directed toward distant sites, I can imagine that the biopsies may have included small fine needle aspiration (FNA) specimens, which probably also have a false-negative rate, especially when the target sites are difficult to sample and if the foci of metastases are small. Thus, some of these PET/CT results may not be false positives."
With this caveat, though, Dr. Vollmer suggests that "PET/CT needs further evaluation in this sentinel-node positive setting."
Dr. Scheier did not respond to a request for comments.
SOURCE: https://bit.ly/1JOemqv
JAMA Oncol 2015.
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