Reporting of Number-Needed-to-Biopsy for Melanoma Varies Widely

Melanoma biopsy under microscopy zoom.
The reported number-needed-to-biopsy for cutaneous melanoma varies widely across clinicians, geography, and patient populations, underscoring the need for uniformity in the metric.

Clinician-reported number needed to biopsy (NNB) for cutaneous melanoma varies widely worldwide, highlighting the need for standardization of NNB and the reporting of the metric, a study in JAMA Dermatology suggests.

A systematic review of the literature was performed, with a focus on including clinical trials that assessed NNB for clinicians on a global scale. In the 46 studies that met the inclusion criteria, the NNB of at least 3681 clinicians and with 455,496 biopsied tumors and 29,257 melanomas were pooled into the final meta-analysis.

Clinician specialization, dermoscopy use, geographic region- and location-specific healthcare system, design of the study, number of benign tumors, number of melanomas, and NNB were all included in the analysis. The primary outcome of interest was the NNB used for the cutaneous melanoma diagnosis.

The pooled data yielded 3 study design strata: all biopsied tumors (stratum A), all melanocytic tumors on pathologic review (stratum B), and clinical concern for melanoma (stratum C).

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In the 3 strata, there was an NNB range of 2.2 to 287 (weighted mean NNB for all, 15.6). Comparatively, the researchers observed an NNB range of 2.2 to 30.5 after excluding studies structured as all biopsied tumors (global weighted mean NNB, 14.8 [clinicians], 7.5 [all dermatologists], 14.6 [Australian primary care practitioners], and 13.2 [US-based dermatological practitioners]).

According to the summary effect size (ES) for each stratum, there was a mean 4% of biopsies that represented melanoma for stratum A (ES, 0.04; 95% CI, 0.03-0.05), as well as a mean 12% of biopsies representing melanoma for strata B (ES, 0.12; 95% CI, 0.10-0.14) and C (ES, 0.12; 95% CI, 0.09-0.14).

Limitations of the study include its retrospective nature, as well as the small amount of data available for clinicians based in the United States.

“Standardization of NNB reporting offers an opportunity to improve the quality of published reports on this important but imperfect metric,” the investigators wrote, “which quantifies the volume of biopsies that result in benign diagnoses in the course of identifying cutaneous melanoma.”

Disclosure: A study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Nelson KC, Swetter SM, Saboda K, Chen SC, Curiel-Lewandrowski C. Evaluation of the number-needed-to-biopsy metric for the diagnosis of cutaneous melanoma: A systematic review and meta-analysis [published online July 10, 2019]. JAMA Dermatol. doi: 10.1001/jamadermatol.2019.1514