Abstract 1203: Incidence of AJCC7 stage III or regionally advanced cutaneous melanoma in the United States

Background: Incidence of stage III/regional melanoma by patient characteristics can help estimate the number of high-risk patients (pts) potentially eligible for adjuvant treatment in a rapidly evolving field and guide the design of future clinical trials based on real-world data. The study describes the incidence of AJCC7 stage III/regional melanoma in the US (a) over time and (b) by melanoma prognostic factors. Methods: Pts newly diagnosed with invasive melanoma were identified in the US Surveillance, Epidemiology, and End Results (SEER) cancer registry (years 2010 -2014; n = 106,195). Stage III melanoma was defined based on the AJCC7 classification (n = 7,669); pts classified as AJCC7 stages I/II but with reported evidence of lymphatic metastasis were considered regionally advanced and included (n =169). Annual incidence was defined as the proportion of individuals in the general population who developed stage III/regionally advanced melanoma over a one-year period (the denominator included the full or age/sex-specific population, as appropriate). Results: During the study period, 7,838 (7.4%) pts were diagnosed with stage III/regional melanoma . The incidence of invasive melanoma has increased from year 2010 to year 2014: from 14.16 to 16.15/100,000 for stages I-IV combined and from 1.25 to 1.50/100,000 for stage III/regional melanoma. Based on the 2014 incidence and the most recent age-specific census population data, it is estimated that 5,109 pts were newly diagnosed in year 2016 with stage III/regional melanoma. In 2014, the incidence of stage III/regional melanoma was higher in elderly than adults and children (incidence per 100,000: 5.16 vs 1.33 and 0.08, respectively) and in males than females (1.79 vs 1.23). Table 1 presents incidence estimates by melanoma characteristics. Conclusions: The results of this analysis indicate an increase in stage III/regional melanoma incidence from 2010 to 2014 and a high incidence of stage III melanoma with poor prognostic factors. Table 1.Stage III1/regional melanomaIncidence in year 20142 (estimate of newly diagnosed in the US in 20163) By tumor thickness4≤ 0.8 mm0.12/ 100,000 population (n=393)0.81 - 1mm0.04 / 100,000 population (n=143)1.01 - 2 mm0.31/ 100,000 population (n=1,028)2.01 - 4 mm0.29/ 100,000 population (n=990)> 4 mm0.37/ 100,000 population (n=1,270)By ulcerationYes0.54/ 100,000 population (n=1,858)No0.62/ 100,000 population (n=2,099)Unknown0.34/ 100,000 population (n=1,152)By number mitoses per s