Reflectance Confocal Microscopy for suspicious lesions can limit unnecessary excisions by almost 50%

Pellacani G, Farnetani F, Ciardo S, Chester J, Kaleci S, Mazzoni L, Bassoli S, Casari A, Pampena R, Mirra M, Lai M, Magi S, Mandel VD, Di Matteo S, Colombo GL, Stanganelli I, Longo C. Effect of Reflectance Confocal Microscopy for Suspect Lesions on Diagnostic Accuracy in Melanoma: A Randomized Clinical Trial. JAMA Dermatol. 2022 Jul 1;158(7):754-761. doi: 10.1001/jamadermatol.2022.1570.

The adjunctive use of RCM resulted in a number needed to excise of 3.0, significantly lower than the number needed to excise with standard therapeutic care (5.3).

Clinical Pearls

• This randomized clinical trial assessed 3165 patients with equivocal lesions suspicious for melanoma. Subjects were assigned to groups with either standard therapeutic care alone or with adjunctive reflectance confocal microscopy (RCM).

• The adjunctive use of RCM resulted in a number needed to excise of 3.0, significantly lower than the number needed to excise with standard therapeutic care (5.3). Additionally, the ratio of benign to malignant excised lesions when using adjunctive RCM was 1.8:1.0, almost half of the ratio when just standard therapeutic care was given (3.7:1.0).

• Overall, this randomized trial found that the use of adjunctive reflectance confocal microscopy for equivocal lesions reduces unnecessary excisions and provides greater accuracy of in-vivo identification of benign lesions.

Discussion:

Reflectance confocal microscopy (RCM) is a novel technique used to provide higher resolution visualization of the skin. The non-invasive nature of RCM may allow it to play a vital role in differentiating benign from malignant lesions. Studies of the clinical application of RCM have been limited to retrospective and prospective observational models, providing results which may overlook the effect of RCM on clinical and therapeutic patient pathways.

The authors performed a prospective randomized interventional study involving 3,165 patients from 3 dermatology referral centers in Italy. Participants were randomized into two groups, one receiving standard therapeutic care plus the use of RCM and the other receiving standard therapeutic care only. The primary outcome used was the number needed to excise (NNE).

Melanoma was identified in 572 of the 3,165 lesions excised and the overall NNE of the study was 4.2. The overall study PPV of an excised lesion being diagnosed as melanoma was found to be 23.9%. The use of adjunctive RCM resulted in a NNE of 3.0, compared to a NNE in the standard therapeutic group of 5.3, resulting in a reduction of 43.2%. The positive predictive value was significantly higher in the treatment group with adjunctive RCM as opposed to the standard therapeutic group (33.3 vs 18.9) as well. Years of RCM experience was found to be very highly correlated with diagnostic accuracy (r=0.99; 95% CI: 0.82-0.99; p = 0.004). In addition, 853 lesions in the adjunctive RCM group were referred to digital dermoscopy follow-up, of which only 15 were diagnosed as melanoma and none were thicker than 0.5mm.

Limitations of this study include its applicability, as only referral centers with RCM experience were included. Additionally, it is not possible to attribute the results of the study to RCM only, as the study design allowed participants in the adjunctive RCM treatment group who did not immediately undergo excision to be assessed with dermoscopy and occasional future RCM assessments. Overall, this study provides promising data about the efficacy and applicability of RCM in the detection of melanoma.