Definition of prognostic subgroups in the T3 stage of the eighth edition of the American Joint Committee on Cancer staging system for cutaneous squamous cell carcinoma: Tentative T3 stage subclassification

Abstract

Although the eighth edition of the American Joint Committee on Cancer staging system (AJCC8) provides improved prognosis stratification of cutaneous squamous cell carcinoma (CSCC) over AJCC7, T3 has a variable prognosis. To define prognostic subgroups in T3-AJCC8 CSCC. Retrospective cohort study of 196 primary T3-AJCC8 CSCCs. We conducted multidimensional scaling analysis using the 6 risk factors that define T3 CSCCs. The prognoses of the groups obtained were analyzed by means of competing risk analysis. Group 1 was characterized by a tumor thickness greater than 6mm (without invasion beyond the subcutaneous fat), alone or in combination with a tumor width of at least 4cm. Group 2 was characterized by the presence of either invasion beyond the subcutaneous fat or by the involvement of nerves (≥0.1mm, or deeper than the dermis). Group 3 was characterized by the combination of both T3b risk factors, or of 3 or more risk factors. Group 3 (tentatively named T3c) patients had the worst prognosis for disease-specific poor outcome events and major events, Group 2 (T3b) had intermediate risk, and Group 1 (T3a) had the best prognosis (disease-specific poor outcome events: hazard ratio [HR], 1.94; P=.00009; major events: HR, 2.55; P=.00001; disease-specific death: HR, 10.25; P=.0009). Retrospective study. There is statistically significant evidence that T3-AJCC8 may be classified into distinct prognostic subgroups.