By Marilynn Larkin
NEW YORK (Reuters Health) - 18/7/2019
The number needed to biopsy (NNB) for cutaneous melanoma varies widely worldwide, and while there isn't a single "ideal" NNB, optimal standards should be developed, researchers say.
"The NNB for cutaneous melanoma is an imperfect metric, as is captures more than just the provider's diagnostic accuracy, or ability to distinguish benign (i.e., normal mole) from malignant (i.e., melanoma)," Dr. Kelly Nelson of MD Anderson Cancer Center in Houston told Reuters Health.
"The NNB is also influenced by the frequency of melanoma in the provider's patient population: if a provider's patients make a lot of melanomas, it takes fewer biopsies to find them," she said by email. "And, conversely, if a provider's patients make very few melanomas, it will take more biopsies to find them."
"Other factors can influence the NNB, including patient anxiety and interpretation patterns for borderline moles with highly atypical features," she noted.
"But, while the NNB is not perfect, it does provide a rough quantification of the number of biopsies performed to find melanomas," she said. "And, when we look at providers in the same practice, assuming the frequency of melanoma is roughly similar across their patients, different providers have different NNBs, suggesting that provider-directed educational efforts could support improvements in NNB."
Further, "using technology, such as total body photography (or 'mole mapping') and being an expert dermoscopist have been shown to be provider-specific skills that support lower NNB," she said.
As reported online July 10 in JAMA Dermatology, Dr. Nelson and colleagues searched the literature from 2000 through 2018 and analyzed 46 studies that addressed NNB for at least 3,681 clinicians worldwide and included 455,496 biopsied tumors and 29,257 melanomas. (Primary care practitioner data were available only from Australia.)
Overall, NNBs ranged from 2.2 to 287, and the weighted mean NNB for all included publications was 15.6.
After excluding publications structured as "all biopsied tumors" because of variable data characterization, NNBs ranged from 2.2 to 30.5. The global weighted mean NNB was 14.8 for all clinicians, 7.5 for dermatologists, 14.6 for Australian PCPs, and 13.2 for all US-based dermatological practitioners, including dermatologists and advanced-practice professionals.
Effect size analyses for three strata of data showed a mean 4% of biopsies demonstrated melanoma among all biopsied skin tumors, and a mean 12% of biopsies demonstrated melanoma for melanocytic tumors on pathology review, and for clinical concern for melanoma.
Summing up, the authors state, "The existing NNB for cutaneous melanoma appeared to vary widely worldwide, lacking standardization in the metric and its reporting, and according to clinician characteristics as well; the NNB of US-based clinicians may warrant further exploration."
"It's important to emphasize that our research does not assert a specific 'ideal' NNB," Dr. Nelson stressed, "as removal of benign nevi can be appropriate and necessary. Instead, we are starting a conversation about the metric and how we can develop appropriate quality metrics for melanoma screening."
Dr. Jeffrey Farma, Co-Director, Melanoma and Skin Cancer Program at Fox Chase Cancer Center in Philadelphia, commented by email, "The findings of this study are interesting but retrospective data in large meta-analyses really should be looked at and confirmed in more specific datasets."
"Ideally there should be overall standards and guidelines on the optimal NNB and this study may help to shed light and achieve such standardization," he told Reuters Health. "This should come from specialty groups and international consortiums to set standards." "Overall, increasing dermatologic education for all practitioners and awareness of skin lesions and diagnostic characteristics will assist with optimizing the NNB," he concluded.
JAMA Dermatol 2019.