title: Patients with both basal and squamous cell carcinomas are at a lower risk of further basal cell carcinomas than patients with only a basal cell carcinoma.
abstract: BACKGROUND
  The rate of development of further basal cell carcinoma (BCC) after first presentation is highly variable. The mechanisms that determine this phenotypic difference are unclear.
  
  
  OBJECTIVE
  We assessed the risks of developing a subsequent BCC in patients who developed a BCC and a squamous cell carcinoma (SCC) and compared them with patients who developed a BCC only.
  
  
  METHODS
  In all, 1040 patients who developed BCC only were compared with 140 patients who developed BCC and SCC to see whether the latter group included a high proportion of risk phenotypes (eg, male sex and fair skin). We then compared the number of BCCs developing per year in the two groups (174 BCC only and 71 BCC/SCC) during a 5-year period after initial BCC presentation.
  
  
  RESULTS
  The BCC/SCC group demonstrated a significantly lower BCC/year rate than BCC only group. The rate of development of further BCC during 5-year follow-up was lower in the BCC/SCC group because a smaller number of patients developed subsequent BCC and not because the same proportion of patients developed lesions but in smaller numbers. After 5 years of follow-up, 51.1% of BCC and 74.6% of BCC/SCC cases were free from a subsequent BCC. Logistic regression analysis corrected for age at initial presentation confirmed that patients with BCC/SCC were less likely to develop a further BCC during the 5 years after initial presentation (P = .001, odds ratio = 0.31, 95% confidence interval 0.15-0.63).
  
  
  CONCLUSIONS
  Because of the large patient group and long study follow-up from the date of the index BCC or SCC, not all data were obtained. Where this is the case, the number of patients for whom the information is available is provided.
  
  
  CONCLUSIONS
  Patients who develop a BCC are similar to patients who develop both a BCC and SCC, confirming the overlap of causative factors. Patients who develop both a BCC and SCC are less likely to develop BCCs compared with patients who develop BCC only.
authors.affiliation: Institute of Science and Technology in Medicine, Keele University Medical School, Hartshill Campus, University Hospital of North Staffordshire, Stoke-on-Trent, United Kingdom.
authors.forename: Sudarshan
authors.initials: S
authors.lastname: Ramachandran
authors.forename: Ratna
authors.initials: R
authors.lastname: Rajaratnam
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Smith
authors.forename: John T
authors.initials: JT
authors.lastname: Lear
authors.forename: Richard C
authors.initials: RC
authors.lastname: Strange
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002280:Basal Cell Carcinoma / Q000453:epidemiology* / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology* / Q000473:pathology; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology* / Q000473:pathology; D009367:Neoplasm Staging; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology* / Q000473:pathology; D016017:Odds Ratio; D011336:Probability; D011379:Prognosis; D018570:Risk Assessment; D017678:Sex Distribution