Nonmelanoma skin cancer and risk of all-cause and cancer-related mortality: a systematic review.

Some reports suggest that a history of nonmelanoma skin cancer (NMSC) may be associated with increased mortality. NMSCs have very low fatality rates, but the high prevalence of NMSC elevates the importance of the possibility of associated subsequent mortality from other causes. The variable methods and findings of existing studies leave the significance of these results uncertain. To provide clarity, we conducted a systematic review to characterize the evidence on the associations of NMSC with: (1) all-cause mortality, (2) cancer-specific mortality, and (3) cancer survival. Bibliographic databases were searched through February 2016. Cohort studies published in English were included if adequate data were provided to estimate mortality ratios in patients with-versus-without NMSC. Data were abstracted from the total of eight studies from independent data sources that met inclusion criteria (n = 3 for all-cause mortality, n = 2 for cancer-specific mortality, and n = 5 for cancer survival). For all-cause mortality, a significant increased risk was observed for patients with a history of squamous cell carcinoma (SCC) (mortality ratio estimates (MR) 1.25 and 1.30), whereas no increased risk was observed for patients with a history of basal cell carcinoma (BCC) (MRs 0.96 and 0.97). Based on one study, the association with cancer-specific mortality was stronger for SCC (MR 2.17) than BCC (MR 1.15). Across multiple types of cancer both SCC and BCC tended to be associated with poorer survival from second primary malignancies. Multiple studies support an association between NMSC and fatal outcomes; the associations tend to be more potent for SCC than BCC. Additional investigation is needed to more precisely characterize these associations and elucidate potential underlying mechanisms.