Satellitosis or in-transit metastasis in cutaneous squamous cell carcinoma: Risk factors and the prognostic significance

Abstract

Background: Satellitosis or in-transit metastasis (S-ITM) from cutaneous squamous cell carcinoma (cSCC) is associated with poor outcomes but is not included in current staging guidelines.

Objective: To determine risk factors and prognostic significance of S-ITM.

Methods: This cohort study included 8901 patients with cSCC from 12 institutions (1998-2023). Risk factors for S-ITM were calculated using logistic regression. Outcomes were compared with 1:2 propensity score matched controls using a Fine-Gray subdistribution hazard model.

Results: Seventy-seven patients developed S-ITM. Increased patient age (odds ratio [OR], 1.03; 95% CI, 1.01-1.05; P < .01), history of immunosuppression (OR, 4.31; 95% CI, 2.59-7.10; P < .001), higher Brigham and Women's Hospital stage (T2a OR, 4.14; 95% CI, 2.05-8.41; T2b OR, 15.96; 95% CI, 8.58-31.19; and T3 OR, 30.27; 95% CI, 10.70-79.04; all P < .001), and lymphovascular invasion (OR, 4.57; 95% CI, 1.80-10.38; P = .001) were independent risk factors for S-ITM. S-ITM was associated with local recurrence (subhazard ratio [SHR], 2.40; 95% CI, 1.43-4.04; P < .001), nodal metastasis (SHR, 1.89; 95% CI, 0.02-3.49; P = .04), distant metastasis (SHR, 4.41; 95% CI, 1.45-13.27; P = .01), and disease-specific death (SHR, 4.48; 95% CI, 2.34-8.58; P < .001).

Limitations: Retrospective cohort study. The rarity of S-ITM may limit statistical power.

Conclusion: Patients with cSCC and S-ITM are at higher risk for poor outcomes independent of patient, tumor, and treatment characteristics.

Keywords: cutaneous squamous cell carcinoma; in-transit-metastases; outcomes; risk factors; satellitosis.