General health versus tumor stage: determinants of survival in Merkel cell carcinoma assessed by sentinel lymph node biopsy.

PURPOSE: Overall survival (OS) of Merkel cell carcinoma (MCC) patients is strongly influenced by health. Sentinel lymph node biopsy (SLNB) is recommended for staging. We evaluated whether SLNB is associated with OS in clinically node-negative MCC and contrasted tumor factors with patient frailty.

METHODS

STROBE-compliant cohort across eight centers in Germany (2004–2024). We included 271 primary stage I–II MCC; 167 underwent SLNB and 104 did not. The primary outcome was OS; disease-specific survival (DSS) and progression-free probability (PFP) were secondary. Kaplan–Meier and Cox models were used. Confounding by indication was addressed with 1:1 propensity score matching and sensitivity analyses.

RESULTS

Patients receiving SLNB were younger (median 74 vs 82 years; p < 0.001) and less comorbid (Charlson 4 vs 5). Ten-year OS was 69.5% with SLNB versus 45.2% without (log-rank p < 0.0001); unadjusted HR 0.34 (95% CI 0.20–0.59). In the matched cohort, SLNB remained associated with lower all-cause mortality (HR 0.56, 95% CI 0.34–0.93; p = 0.024). DSS did not differ (HR 1.09, 95% CI 0.55–2.13;  p= 0.81). For PFP, unadjusted curves favored SLNB (p=0.0045), but the matched analysis was not significant (HR 0.53, 95% CI 0.23–1.26). Sensitivity analyses suggested benefit: overlap weighting HR 0.49 (95% CI 0.33–0.73; p = 0.00045) and a stage-restricted match HR 0.36 (95% CI 0.13–0.99; p= 0.048).

CONCLUSIONS

SLNB was associated with improved OS after adjustment, supporting its role in staging and risk stratification. The absence of DSS and matched PFP differences highlights the influence of overall health; residual confounding by indication cannot be excluded.