To assess the risk of developing a basal cell carcinoma (BCC), and/or a squamous cell carcinoma (SCC), and/or Bowen disease (SCC in situ) after a nonmelanoma skin cancer (NMSC) of a specific type.
Four eletronic databases were searched from January 1, 1966, to October 21, 1999.
We included all studies published in English, identified by standard search strategies, that provided original data quantifying the risk of an NMSC among persons with a previous NMSC.
For each study and separate histological type of index skin tumor and subsequent skin tumor (SCC, BCC, NMSC, or Bowen disease), we determined the 3-year cumulative risk and the incidence rate of second tumors per 100 000 person-years. In cases where more than 1 study was assessing the risk of one specific tumor type after another, we undertook a formal meta-analysis. We compared the incidence of a subsequent SCC after an index SCC and of a subsequent BCC after an index BCC with the incidence of the first occurrence of such tumors in the comparable general population.
We identified and reviewed 17 studies that included data for 26 tumor combinations. Overall, the 3-year cumulative risk of a subsequent SCC after an index SCC is 18%, at least a 10-fold increase in incidence compared with the incidence of first tumors in a comparable general population. For BCCs, the 3-year cumulative risk is 44%, also at least a 10-fold increase in incidence compared with the rate in a comparable general population. The risk of developing a BCC in patients with a prior SCC is about equal to that risk among persons with a prior BCC, but the risk of developing an SCC in patients with a prior BCC is low (6%).
Although these studies vary in their study type, location, and biases, their results are consistent. The risk of developing a subsequent skin cancer of a specific type depends on the type of prior NMSC and number of prior skin tumors of that type. Based on these findings, follow-up strategies for patients with BCC and SCC are suggested.