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 and 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. What's new? Even though keratinocyte cancers rarely metastasize and are generally curable, they increase the likelihood of subsequent cancer or death. What's going on? To investigate, these authors followed up cancer survivors over a period of more than 10 years. Both types of keratinocyte cancer (basal and squamous cell carcinoma) led to an uptick in later cancer risk. Curiously, survivors of BCC had no increase in mortality rate, while those who survived SCC had a 25% increase in mortality. Clearly, then, the mortality hike isn't due to subsequent cancer. What does cause it remains unclear.