Effectiveness of SPECT/CT imaging for sentinel node biopsy staging of primary cutaneous melanoma and patient outcomes

Purpose: Coregistered SPECT/CT can improve accuracy of sentinel node biopsy (SNB) for staging melanoma. This benefit has implications for pathology services and surgical practice with increased diagnostic and surgical workload. The purpose of this study was to investigate the effectiveness of SPECT/CT imaging. 

Methods: SNB data were collected over a 10-year period. Preoperative SLN mapping was performed by using planar lymphoscintigraphy (LSG) for all patients (n = 1522) and after October 2015, patients underwent a second co-registered SPECT/CT scan (n = 559). The patients were stratified according to the imaging protocol. The number of nodes and nodal basins were assessed. The reasons for cancellation also were assessed. 

Results: A total of 95% (1446/1522) of patients underwent a successful SNB procedure. Significantly more sentinel nodes were identified by the SPECT/CT protocol (3 vs. 2; p < 0.0001). More patients were cancelled in the SPECT/CT cohort (9.3% vs. 2.5%; p < 0.0001). Head & neck, lower limb, and AJCC IB primaries were significantly less likely to proceed to SNB. SPECT/CT identified significantly more positive SNBs (20.9% vs. 16.5%; p = 0.038). SPECT/CT imaging was associated with improved disease-free (hazard ratio [HR] = 0.74; 95% confidence interval [CI]: 0.54–1.0); p = 0.048) and disease-specific survival (HR = 0.48; 95% CI: 0.3–0.78; p = 0.003). Patients who did not proceed to SNB had a significantly increased nodal relapse rate (23.5% vs. 6.8%; HR = 3.4; 95% CI: 1.9–6.2; p < 0.0001) compared with those who underwent SNB. 

Conclusions: This large cohort study confirms the increased accuracy of SPECT/CT for identifying SLN metastases, which would appear to have a significant therapeutic benefit, although an increased risk of cancellation of the SNB procedure on the day of surgery.