Survival after squamous cell and basal cell carcinoma of the skin: A retrospective cohort analysis

A retrospective cohort analysis of survival after keratinocyte cancer (KC) was conducted using data from a large, population-based case control study of KC in New Hampshire. The original study collected detailed information during personal interviews between 1993-2002 from individuals with squamous (SCC) and basal (BCC) cell carcinoma, and controls identified through the Department of Transportation, frequency-matched on age and sex. Participants without a history of non-skin cancer at enrolment were followed as a retrospective cohort to assess survival after either SCC or BCC, or a reference date for controls. Through 2009, cancers were identified from the New Hampshire State Cancer Registry and self-report; death information was obtained from state death certificate files and the National Death Index. There were significant differences in survival between those with SCC, BCC and controls (p=0.040), with significantly greater risk of mortality after SCC compared to controls (adjusted hazard ratio [HR] 1.25; 95% confidence interval 1.01-1.54). Mortality after BCC was not significantly altered (HR 0.96; 95% CI 0.77-1.19). The excess mortality after SCC persisted after adjustment for numerous personal risk factors including time-varying non-skin cancer occurrence, age, sex and smoking. Survival from the date of the intervening cancer, however, did not vary (HR for SCC 0.98; 95% CI 0.70-1.38). Mortality also remained elevated when individuals with subsequent melanoma were excluded (HR for SCC 1.30; 95% CI 1.05-1.61). Increased mortality after SCC cannot be explained by the occurrence of intervening cancers, but may reflect a more general predisposition to life threatening illness that merits further investigation.