Patency Capsule: A Novel Independent Predictor for Long-Term Outcomes Among Patients With Quiescent Crohn's Disease.

INTRODUCTION: Patency capsule (PC) is a recommended procedure to rule out small bowel stenosis before video capsule endoscopy (VCE). We examined future clinical outcomes among patients with a failed PC vs patients in whom the PC had passed (passed PC). METHODS: A post hoc analysis of 2 prospective cohort studies of adult patients with quiescent small bowel Crohn's disease (CD) who underwent PC between 2013 and 2020. The primary composite outcome was the need for intestinal surgery or endoscopic dilation during follow-up in patients with or without a failed PC. RESULTS: A total of 190 patients were included (47: failed PC and 143: passed PC, median follow-up 34.12 months). Patients with a failed PC had higher rates of the primary composite outcome (21.3% vs 1.4%, hazard ratio [HR] 20.3, 95% confidence interval [CI] 4.4-93.7, P < 0.001) and also secondary outcomes including intestinal surgery (14.9% vs 0.70%, P < 0.001), endoscopic dilation (14.9% vs 0.70%, P < 0.001), admissions (23.3% vs 5.7%, P < 0.001), and clinical flares (43.9% vs 27.7%, P = 0.005) during follow-up compared with controls. Failed PC was the only statistically significant factor for surgery and/or endoscopic dilation, regardless of a B2/B3 phenotype at baseline. In sensitivity analyses restricted only to patients with a stricturing phenotype (n = 73), a failed PC still predicted the long-term composite outcome (HR 8.68, 95% CI 1.72-43.68, P = 0.002). Of the 190 patients ingesting a PC, only 1 patient with a failed PC had 48 hours of self-limiting mild symptoms. DISCUSSION: Patients with clinically stable CD with a failed PC have worse long-term clinical outcomes than those without, independently of the CD phenotype. Standalone PC may serve as a novel, safe, and affordable prognostic examination to identify patients with quiescent CD who have a higher risk for future worse clinical outcomes.

Prospective Observational Evaluation of Time-Dependency of Adalimumab Immunogenicity and Drug Concentrations: The POETIC Study.

OBJECTIVES: Adalimumab is usually self-injected at home, making prospective serial-sampling studies challenging and scarce. This has led to a gap in knowledge about evolution of anti-adalimumab antibodies (AAAs) over time and its correlation with clinical and inflammatory outcomes. METHODS: A program for home visits by physicians at induction, every 3 months and at event of relapse, was established prospectively for Crohn's disease (CD) patients. At each visit, patients' clinical scores were determined and sera were obtained for C-reactive protein, drug, and AAA levels. This cohort was compared to a parallel prospective cohort of infliximab-treated CD patients. In a subgroup of 29 patients, trough and in-between-trough levels were compared, to elucidate the importance of timing of sampling during the injection cycle. RESULTS: Ninety-eight CD patients starting adalimumab were prospectively followed (median follow-up 44 weeks) and 621 serum samples were analyzed. Thirty-three patients (32%) developed AAA; 18/33 (55%) of them as early as week 2, and 26/33 (79%) by week 14. Induction period AAAs were strongly associated with primary non-response (odds ratio (OR) = 5.4, 95% confidence interval (CI): 1.6-17.8, p = 0.005). As compared to antibodies-to-infliximab (ATI), AAA formation rate over time was significantly lower (p = 0.01) and AAA were much more specific-85% of AAA events were associated with loss-of-response compared with 58% rate for ATI (p = 0.01). In 29 patients sampled serially during an injection cycle, levels of drug and AAA seemed comparable between four time-points during a single cycle both in patients with or without AAA (n = 8, n = 21, respectively). CONCLUSIONS: When followed prospectively and serially, AAAs are found to arise earlier than previously appreciated and their impact may be more pronounced for primary rather than secondary, non-response. Drug and AAA levels were similar both at trough and in-between injections, enabling to simplify therapeutic drug monitoring of adalimumab.

Prospective Observational Evaluation of the Time-Dependency of Adalimumab Immunogenicity and Drug Concentration in Ulcerative Colitis Patients: the POETIC II Study.

BACKGROUND AND AIMS: Home self-injection of the human anti-tumour necrosis alpha [anti-TNFα] monoclonal adalimumab complicates prospective serial-sampling studies. Although a recent study examined adalimumab levels and immunogenicity in Crohn's disease [CD] patients, prospective real-world data from ulcerative colitis [UC] patients are lacking. METHODS: A three-monthly home-visit programme from induction was established prospectively for UC patients. Clinical scores were determined at each visit, and sera were obtained for assessment of drug and anti-adalimumab antibody levels. Calprotectin was measured using a smartphone-based app. This cohort was compared to a parallel prospective cohort of adalimumab-treated CD patients [POETIC1]. RESULTS: Fifty UC patients starting adalimumab [median follow-up 28 weeks] were compared to 98 adalimumab-treated CD patients [median follow-up 44 weeks]. Only 11/50 UC patients [22%] continued treatment to the end of the follow-up compared with 50/98 [51%] CD patients (odds ratio [OR] = 0.27, p = 0.001). Loss of response was significantly more common in UC patients [OR = 3.2, p = 0.001]. Seventeen patients [34%] in the UC cohort developed anti-adalimumab antibodies, 9/17 [52.9%] as early as week 2. There was no difference between patient cohorts in the overall development of anti-adalimumab antibodies [34% vs 30.6%, respectively, OR = 1.67, p = 0.67], nor was there a difference in early immunogenicity [OR = 1.39, p = 0.35]. There was no difference in low drug levels [<3 µg/mL] between the two cohorts [OR = 0.87, p = 0.83]. CONCLUSIONS: Loss of response to adalimumab therapy was significantly more common in the UC compared to the CD cohort and was driven by a higher rate of non-immunogenic, pharmacodynamic parameters.

Middle small-bowel segment Lewis score may predict long-term outcomes among patients with quiescent Crohn's disease.

Background: Video capsule endoscopy (VCE) has been proven to accurately diagnose small-bowel inflammation and predict flares among patients with quiescent Crohn's disease (CD). However, data regarding its predictive role in this population over an extended follow-up are scarce. Objectives: To predict clinical exacerbation and to assess the yield of Lewis score in identifying CD patients with future clinical exacerbation during an extended follow-up (>24 months). Design: A post hoc analysis study. Methods: Adult patients with quiescent small-bowel CD who were followed with VCE, inflammatory biomarkers and magnetic resonance enterography in a prospective study (between 2013 and 2018). We extracted extended clinical data (up to April 2022). The primary composite outcome (i.e. clinical exacerbation) was defined as intestinal surgery, endoscopic dilation, CD-related admission, corticosteroid administration, or biological/immunomodulator treatment change during follow-up. Results: Of the 61 patients in the study [median age 29 (24-37) years, male 57.4%, biologic treatment 46.7%], 18 patients met the primary outcome during an extended follow-up [median 58.0 (34.5-93.0) months]. On univariable analysis, complicated [hazard ratio (HR) 7.348, p = 0.002] and stricturing disease phenotype (HR 5.305, p = 0.001) were associated with higher risk for clinical exacerbation during follow-up. A baseline VCE middle small-bowel segment Lewis score (midLS) ⩾ 135 identified patients with future exacerbation [AUC (area under the curve) 0.767, 95% confidence interval (CI) 0.633-0.902, p = 0.001, HR 6.317, 93% negative predictive value], whereas the AUC of the conventional Lewis score was 0.734 (95% CI: 0.589-0.879, p = 0.004). Sensitivity analysis restricted to patients with either complicated (n = 34) or stricturing (n = 26) disease phenotype revealed that midLS still predicted clinical exacerbation during follow-up (AUC 0.747/0.753, respectively), in these patients. Conclusion: MidLS predicts treatment failure in quiescent CD patients (median follow-up of 5 years) independently of disease phenotype.

Delaying an infliximab infusion by more than 3 days is associated with a significant reduction in trough levels but not with clinical worsening.

Background: Higher infliximab trough levels (TLs) correlate with better clinical, inflammatory, and endoscopic outcomes among inflammatory bowel disease (IBD) patients. Although standard scheduled infliximab therapy regimen consists of infusions at pre-defined time-points (weeks 0, 2, 6, and every 8 weeks), short-period deviations from therapeutic schedule are common in 'real life', but the pharmacokinetic impact of these deviations has not been explored. In this study, we aim to determine whether short-period deviations from infusion schedule affect infliximab-TL. Methods: A retrospective analysis of all IBD patients receiving infliximab maintenance therapy every 8 weeks was conducted in a tertiary medical center. Patients with anti-drug antibodies, deliberate interval shortening and <3 sequential maintenance sera available were excluded. Associations between time since last infusion and TL were studied. Statistical analysis was performed using generalized estimating equations. Results: Out of over 10,000 sera, 2088 sera of 302 maintenance period stable infliximab-therapy-patients met inclusion criteria (median TL 4.1 µg/mL, interquartile range (IQR) 2.3-6.5 µg/mL). A delay beyond 3 days in infusion schedule (n > 59 days since last infusion) was found to significantly affect TL (mean difference in TL 0.9 µg/mL, 95% confidence interval (CI): 0.03-1.9 µg/mL, p < 0.04). Furthermore, among patients with delayed infusions, 80% had TL below 5 µg/mL, in comparison to 55% of patients who were not late (odds ratio (OR): 2.81, CI: 2.02-3.92, p < 0.0001). Conclusion: Real-life delays of ⩽3 days from infusion protocol can probably be allowed. Delays >3 days culminate in measurable decrease of TL, although effect on clinical outcome is unclear. This needs to be taken into account when interpreting drug-level test results. Summary: A total of 2088 sera of 302 maintenance period inflammatory bowel disease (IBD) patients treated with infliximab were analyzed, to assess effect of small deviations from infusion schedule on TLs. A significant decline in patients' trough level (TL) was noted as early as 3 days after scheduled infusion.

Serum Syndecan-1: A Novel Biomarker for Pancreatic Ductal Adenocarcinoma.

INTRODUCTION: Syndecan-1 (SDC1) has multiple functions in tumorigenesis in general and specifically in pancreatic cancer. We aimed to evaluate SDC1 as a diagnostic and prognostic biomarker in patients with pancreatic ductal adenocarcinoma (PDAC). METHODS: In this case-control study, patients newly diagnosed with a biopsy-proven PDAC were enrolled alongside healthy individuals in a derivation-validation cohort design. Serum SDC1 was measured by enzyme-linked immunoassay. The diagnostic accuracy of SDC1 levels for diagnosing PDAC was computed. A unified cohort enriched with additional early-stage patients with PDAC was used to evaluate the association of SDC1 with survival outcomes and patient characteristics. RESULTS: In the derivation cohort, serum SDC1 levels were significantly higher in patients with PDAC (n = 39) compared with healthy controls (n = 20) (40.1 ng/mL, interquartile range 29.8-95.3 vs 25.6 ng/mL, interquartile range 17.1-29.8, respectively; P < 0.001). The receiver operating characteristic analysis area under the curve was 0.847 (95% confidence interval 0.747-0.947, P < 0.001). These results were replicated in a separate age-matched validation cohort (n = 38 PDAC, n = 38 controls; area under the curve 0.844, 95% confidence interval 0.757-0.932, P < 0.001). In the combined-enriched PDAC cohort (n = 110), using a cutoff of 35 ng/mL, the median overall 5-year survival between patients below and above this cutoff was not significantly different, although a trend for better survival after 1 year was found in the lower level group (P = 0.06). There were 12 of the 110 patients with PDAC (11%) who had normal CA 19-9 in the presence of elevated SDC1. DISCUSSION: These findings suggest serum SDC1 as a promising novel biomarker for early blood-based diagnosis of pancreatic cancer.

Dose optimisation for Loss of Response to Vedolizumab- Pharmacokinetics and Immune Mechanisms.

BACKGROUND: Real life data regarding pharmacokinetics of vedolizumab in patients needing dose optimisation are scarce. We set to examine whether pre-optimisation vedolizumab levels associate with therapy outcomes and which mechanisms explain the associations. METHODS: A multicentre observational study assessed the outcome of dose increase in association with pre-escalation levels in vedolizumab-treated patients. SubsequentIy, α4ß7 occupancy on peripheral blood [PB] and intestinal lamina propria [LP] tissues was investigated on various cellular subsets in patients undergoing lower endoscopy on infusion day. Cellular localisation of vedolizumab-bound α4ß7 and effects on M1 and M2 macrophages were also explored. RESULTS: A total of 161 inflammatory bowel disease [IBD] patients were included. Among 129/161 patients intensified during maintenance [Week 14 onward], pre-intensification trough levels were comparable or higher among those subsequently attaining post-optimisation clinical, biomarker, and endoscopic remission, compared with non-remitting patients [p = 0.09, 0.25, 0.04, respectively]. Similar results were demonstrated for those dose-optimised during induction [Week 6, n = 32]. In the immune sub-study [n = 43], free α4ß7 receptors at trough were similarly low among patients with/without mucosal healing, on PB T cells [p = 0.15], LP T cells [p = 0.88], and on PB eosinophils [p = 0.08]. Integrin receptors on M1 and M2 macrophages were also saturated by low levels of vedolizumab and anti-inflammatory cytokine secretion was not increased. Co-localisation and dissociation experiments demonstrated membranal α4ß7 receptors of two origins: non-internalised and newly generated α4ß7, but re-binding was still complete at very low concentrations. CONCLUSIONS: These results do not support pharmacokinetics as the mechanism responsible for loss of response to vedolizumab, nor do they support a need for higher drug concentration to enhance vedolizumab's immune effects. Higher pre-escalation levels may indicate less clearance [less severe disease] and higher likelihood of subsequent re-gained response, regardless of therapy escalation.

A novel PillCam Crohn's capsule score (Eliakim score) for quantification of mucosal inflammation in Crohn's disease.

INTRODUCTION: Capsule endoscopy is an important modality for monitoring of Crohn's disease. Recently, a novel panenteric capsule, PillCam Crohn's (Medtronic, USA), was approved for use. No quantitative index of inflammation for this method is currently available. This sub-study of a prospective randomized controlled Comprehensive individUalized pRoactive ThErapy of Crohn's Disease trial (CURE-CD) which aimed to compare the correlation and reliability of the novel PillCam Crohn's score with the existing small bowel capsule Lewis inflammatory score. METHODS: The study cohort included Crohn's disease patients in remission who were evaluated with PillCam Crohn's. Each result was independently reviewed by two experienced readers. Inflammation was scored in all studies using Lewis inflammatory score and PillCam Crohn's score (comprised of a sum of scores for most common and most severe lesions multiplied by percentage of segmental involvement + stricture score). RESULTS: Fifty-four PillCam Crohn's studies from 41 patients were included. The median Lewis inflammatory score was 225 for both readers. The median PillCam Crohn's score was six (0-14) and four (3-15) for readers 1 and 2, respectively. There was a high inter-rater reliability coefficient between the two readers for Lewis inflammatory and PillCam Crohn's score (0.9, p < 0.0001 for both). The correlation between PillCam Crohn's score and fecal calprotectin was stronger than for Lewis inflammatory score (r = 0.32 and 0.54 respectively, p = 0.001 for both). CONCLUSIONS: The novel panenteric capsule score correlates well with the Lewis inflammatory score, has excellent reliability, and may be potentially more accurate in estimation of the panenteric inflammatory burden.

Lower adalimumab trough levels are associated with higher bowel wall thickness in Crohn's disease.

BACKGROUND: In Crohn's disease, higher adalimumab trough levels and negative anti-adalimumab-antibodies associate with better clinical and endoscopic outcomes. Intestinal ultrasound has become a relevant non-invasive method to monitor treatment. However, data on the association between adalimumab levels and bowel wall thickness measured with ultrasound is limited. OBJECTIVE: The purpose of this study was to examine the possible association between the sonographic transmural-thickness and adalimumab trough levels. METHODS: This prospective observational cohort study was conducted at Sheba Medical Center in 2014-2018. Crohn's disease patients on adalimumab maintenance therapy with intestinal ultrasound performed within <30 days of trough level measurement were included. Associations between terminal ileum and colonic thickness, adalimumab levels and therapy retention were assessed. RESULTS: Fifty events of ultrasound with concomitant adalimumab trough level measurements in 44 Crohn's disease patients were included. Patients with trough level <3 µg/ml had significantly higher bowel wall thickness, both for terminal ileum (p = 0.04) and colon (p = 0.02). Thirty-two patients continued adalimumab therapy over one year. The adalimumab retention rate was higher among those with terminal ileum thickness <4 mm (p = 0.03). CONCLUSION: Lower adalimumab trough levels were associated with higher bowel wall thickness indicating poorer therapy outcome. Transmural thickness measurement with ultrasound may be a useful target for guiding biologic therapy in Crohn's disease.

Serum MMP-9: a novel biomarker for prediction of clinical relapse in patients with quiescent Crohn's disease, a post hoc analysis.

BACKGROUND: Matrix metalloproteinase-9 (MMP-9) is a novel marker of intestinal inflammation. The aim of this study was to assess if serum MMP-9 levels predict clinical flare in patients with quiescent Crohn's disease (CD). METHODS: This study was a post hoc analysis of a prospective observational study in which quiescent CD patients were included and followed until clinical relapse or the end of a 2-year follow-up period. Serial C-reactive protein (CRP) and fecal calprotectin (FC) levels were measured, and the patients underwent repeated capsule endoscopies (CEs) every 6 months. Small bowel inflammation was quantified by Lewis score (LS) for CE. A baseline magnetic resonance enterography was also performed, and MaRIA score was calculated. Serum MMP-9 levels in baseline blood samples were quantified by ELISA. RESULTS: Out of 58 eligible enrolled patients, 16 had a flare. Higher levels of baseline MMP-9 were found in patients who developed subsequent symptomatic flare compared with patients who did not [median 661 ng/ml, 25-75 interquartile range (IQR; 478.2-1441.3) versus 525.5 ng/ ml (339-662.7), respectively, p = 0.01]. Patients with serum MMP-9 levels of 945 ng/ ml or higher were at increased risk for relapse within 24 months [area under the curve (AUC) of 0.72 [95% confidence interval (CI): 0.56-0.88]; hazard ratio 8.1 (95% CI 3.0-21.9, p < 0.001)]. Serum MMP-9 concentrations showed weak and moderate correlation to baseline LS and FC, respectively (r = 0.31, p = 0.02; r = 0.46, p < 0.001). No correlation was found between serum MMP-9 to CRP and MaRIA score. CONCLUSIONS: Serum MMP-9 may be a promising biomarker for prediction of clinical flare in CD patients with quiescent disease.

Assessment of small bowel mucosal healing by video capsule endoscopy for the prediction of short-term and long-term risk of Crohn's disease flare: a prospective cohort study.

BACKGROUND: The optimal monitoring strategy for predicting disease course in Crohn's disease remains undefined. We aimed to evaluate the accuracy, safety, and tolerability of an intensive monitoring strategy designed to predict the future course of Crohn's disease in patients with quiescent disease. METHODS: In a prospective observational cohort study, we recruited patients older than 18 years with quiescent (for 3-24 months) Crohn's disease involving the small bowel with confirmed small bowel patency from three tertiary medical centres in Israel. Enrolled patients underwent baseline magnetic resonance enterography (MRE) and patency capsule, clinical or biomarker assessment every 3 months, and video capsule endoscopy (VCE) at baseline and every 6 months for 2 years or until a clinical flare (the primary outcome, defined as an increase in the Crohn's disease activity index score by 70 points or more) or disease worsening necessitating treatment intensification. We assessed the ability of the different Crohn's disease monitoring methods used to predict the occurrence of a flare during the 24-month follow-up period. FINDINGS: Of 90 screened patients, 29 were excluded (17 because of non-patent small bowel). Of the 61 patients enrolled between July 3, 2013, and Feb 1, 2015, 17 (28%) had a flare during the 24-month follow-up. No clinicodemographic parameter predicted future flare. A baseline VCE Lewis score of 350 or more identified patients with future flare (area under the curve [AUC] 0·79, 95% CI 0·66-0·88; p<0·0001; hazard ratio 10·7, 3·8-30·3). C-reactive protein at baseline had an AUC of 0·73 (0·6-0·84; p=0·0013) for predicting flare. The AUC of baseline faecal calprotectin for the prediction of flare occurring within 2 years was 0·62 (0·49-0·74; p=0·17), but progressively improved for shorter timespans and reached an AUC of 0·81 (0·76-0·85) for the prediction of flare occurring within 3 months. Of four MRE-based indices, only MRE global score correlated with 2-year flare risk (AUC 0·71, 0·58-0·82; p=0·024). During follow-up, a Lewis score increase of 383 points or more from baseline predicted imminent disease exacerbation within 6 months (AUC 0·79, 0·65-0·89; p=0·011). The safety and tolerability of the 231 VCEs ingested was excellent, with none being retained. INTERPRETATION: In patients with quiescent Crohn's disease involving the small bowel, faecal calprotectin predicts short-term flare risk, whereas VCE predicts both short-term and long-term risk of disease exacerbation. If corroborated by additional studies, protocols incorporating VCE could expand the scope of available methods for monitoring disease activity and predicting outcomes in small bowel Crohn's disease. FUNDING: The Leona M & Harry B Helmsley Charitable Trust.

Vedolizumab Levels in Breast Milk of Nursing Mothers With Inflammatory Bowel Disease.

INTRODUCTION: There are no data on the transfer of vedolizumab in breast milk of nursing mothers. We aimed to assess the presence of vedolizumab in breast milk of nursing inflammatory bowel disease [IBD] patients. METHODS: This was a prospective observational study of vedolizumab-treated breastfeeding patients with IBD. Serum and breast milk samples were obtained at pre-defined tim -points. The in-house developed enzyme-linked immunosorbent assay [ELISA] for measuring vedolizumab in blood was adapted and validated for measurement of the drug in breast milk. The level of vedolizumab was also measured in breast milk of a control group of nursing healthy mothers. RESULTS: Vedolizumab was undetectable in breast milk in IBD patients before the first infusion of vedolizumab [n = 3] and in all of the healthy controls [n = 5]. Vedolizumab was measurable in all lactating women who received vedolizumab [n = 5]. However, on serial measurements in breast milk after an infusion, drug levels did not surpass 480 ng/ml, which was roughly 1/100 of the comparable serum levels. CONCLUSIONS: Vedolizumab can be detected in the breast milk of nursing mothers. Although more data are imperative, the concentrations of vedolizumab in breast milk are minute and are therefore unlikely to result in systemic or gastro-intestinal immune-suppression of the infant.

Precise Longitudinal Tracking of Microscopic Structures in Melanocytic Nevi Using Reflectance Confocal Microscopy: A Feasibility Study.

IMPORTANCE: Reflectance confocal microscopy (RCM), a cellular-level, in vivo imaging technique, may be potentially used for monitoring melanocytic neoplasms for microscopic stability vs changes over time. OBJECTIVE: To test feasibility of using RCM to track specific microscopic structures within nevi over 1 year. DESIGN, SETTING, AND PARTICIPANTS: This was an observational study, a review of prospectively acquired RCM images, performed at a tertiary academic medical center. Seventeen patients were enrolled from adult patients presenting to pigmented lesion clinic; from each participant, 3 confirmed benign nevi were randomly selected from the upper and lower back and from the lower extremity. EXPOSURES: Nevi underwent standardized RCM imaging at baseline and after 1 year. MAIN OUTCOMES AND MEASURES: We tested interobserver reproducibility in recognition of tissue anchors, RCM structures that can be identified at 2 time points. We used 2 tests to measure concordance between independent readers: (1) In the multiple choice matching test (n = 43 nevi), readers were shown a tissue anchor in a baseline RCM image (≤ 1 × 1-mm field-of-view) and asked to identify the same structure in 1 of 4 equally sized RCM images obtained from the same nevus at follow-up. (2) In the annotation test (n = 29 nevi), readers were shown a tissue anchor in a follow-up RCM image (≤ 1 × 1-mm field-of-view) and asked to annotate the corresponding location of this structure in the baseline RCM mosaic image (≤ 5 × 5-mm field-of-view) from the same nevus; good agreement was defined as annotations deviant by less than 10% of the mosaic's width. RESULTS: In total, 17 patients (mean age, 45 years [range, 28-70 years]; 10 [59%] were women) contributed a total of 51 nevi, of which 44 nevi (86%) were used for the study. Images from 7 nevi (14%) were suboptimal in quality. Tissue anchors were identified at both time points in all 44 nevi. Selected tissue anchors were located at a mean depth of 54.3 µm; the most commonly selected anchors (37 of 44 images [84.1%]) were dermal papillae. In the multiple choice matching test, compared with a reference reader, 2 readers correctly matched baseline to follow-up tissue anchors in 40 of 43 nevi (93%; P < .01) and 42 of 43 nevi (98%; P < .01), respectively. In the annotation test, there was good agreement between 2 readers in all 29 cases (100%); the mean deviation was 2% (range, 0%-7.5%). CONCLUSIONS AND RELEVANCE: Precise longitudinal tracking of microscopic structures in melanocytic nevi using RCM is feasible.