Response to ‘A call to standardize the BCC:SCC ratio’: reply from the authors

Abstract

BCC) to squamous cell carcinoma (SCC) by accounting for tumour-based incidence, age, sex and latitude of residence. 1 Through uniform calculation, ratios can be compared across populations and over time, to monitor trends and identify risk factors. 1 The authors present a strong argument for the standardization of the ratio. However, we believe that SCC in situ (SCCis) should be included in the calculation of the incidence rate ratio (IRR). Management of SCCis is often analogous to superficial BCC. Both can be treated with topical imiquimod, cryotherapy, electrodessication and curettage, excision or Mohs micrographic surgery. 2,3 Similar to the low risk of superficial BCC becoming invasive, the chance of SCCis progressing to invasive SCC is also slim, with a reported rate of 3-5%. 3,4 Although SCCis may not progress to invasive SCC frequently, high-risk locations such as the genitalia and lips, immunosuppression and depth of follicular extension often necessitate more aggressive treatment. 3 Given the treatment similarity between SCCis and superficial BCC, and the possibility of high-risk features associated with SCCis, we believe the calculation for IRR is more accurate if the equation is modified: