Risk factors for development of new skin neoplasms in patients with past history of skin cancer: A survival analysis.

We conducted a retrospective study aiming to assess the risk, and associated risk factors, of developing subsequent skin cancers after having a first diagnosis of skin cancer. We included all patients with biopsy-proven skin cancer attending a dermatology clinic between July 2007 and July 2017. We assessed the frequency of new skin cancers, as well as potential demographic and clinical factors significantly associated with occurrence of such neoplasms, that were identified by means of a survival analysis. We analyzed 969 patients with a total of 1584 skin neoplasms (1122 basal cell carcinomas (BCC), 310 squamous cell carcinomas (SCC), 143 melanomas and 9 other neoplasms). 165 patients (17.0%) developed subsequent skin neoplasms. Factors identified in multivariable models to be significantly associated with development of new skin cancers included older age (adjusted HR = 1.04 per year; 95%CI = 1.02-1.05; p < 0.001), and presence of synchronous neoplasms (adjusted HR = 2.25; 95%CI = 1.61-3.14; p < 0.001). Having a history of a BCC was significantly associated with development of new BCC (adjusted HR = 1.63; 95%CI = 1.05-2.54; p = 0.030), while having a previous SCC was associated with occurrence of subsequent SCC (adjusted HR = 3.60; 95%CI = 1.93-6.72; p < 0.001). These findings point to the importance of careful follow-up (e.g., skin self-examination and full body examination) of skin cancer patients.