Metastasis of cutaneous squamous cell carcinoma in organ transplant recipients and the immunocompetent population: is there a difference? a systematic review and meta-analysis

Background Organ transplant recipients (OTR) have a higher risk of developing cutaneous squamous cell carcinoma (cSCC) compared to the immunocompetent population. Immunosuppression is often stated as a risk factor for metastasis. However, evidence for this is scarce. Objectives To investigate the cSCC metastasis risk in OTR and the immunocompetent population by systematically reviewing the literature. Methods A systematic review of the literature was performed up to January 2018 using: Medline; Embase; Web of Science and ISI Science Citation Index. Studies assessing cSCC metastasis risk in ORT or immunocompetent cohorts were considered. A pooled risk estimate for metastasis was calculated for the immunocompetent population and OTR separately. Results The pooled metastasis risk estimate for OTR was, respectively, 7.3% (95% CI 6.2–8.4) for cSCC on total body, and 11.0% (95% CI 7.7–14.8) for cSCC of the head neck area. For the immunocompetent population reported risk estimate analysis showed a pooled metastatic risk of 3.1% (95% CI 2.8–3.4) in total body cSCC and of 8.5% (95% CI 7.3– 9.8) in cSCC of the head and neck area. Pooled risk estimate per single cSCC in OTR was 1.3% (95% CI 1.0–1.7) in total body cSCC and 4.0% (95% CI 2.7–5.5) in cSCC of the head and neck area. In the immunocompetent population, these pooled risk estimates were, respectively, 2.4% (95% CI 2.1–2.6) and 6.7% (95% CI 5.7–7.8). Conclusions Organ transplant recipients show a higher overall risk of cSCC metastasis compared to the immunocompetent population. Metastasis risks per single cSCC were substantially lower in both groups. However, due to heterogeneity and differences between studies, comparisons are difficult. Comprehensive follow-up studies with defined cohorts are necessary to adequately asses the risk for cSCC metastasis.

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