Brigham and Women's Hospital tumor classification system for basal cell carcinoma identifies patients with risk of metastasis and death

Background: Despite approximately 4400 locally advanced US cases annually, high-stage basal cell carcinoma (BCC) is ill-defined. Objective: To develop a tumor (T) staging system for BCC that will predict metastasis/death and compare its performance with that of the American Joint Committee on Cancer 8th edition (AJCC8) T-staging system. Methods: Brigham and Women's Hospital (BWH) T staging was developed from a previously published nested cohort of 488 primary BCCs. Tumors were staged via BWH and AJCC8 T-staging systems, and predictions of metastasis and/or death were compared. Results: The BWH and AJCC8 T-staging systems both captured all metastases/deaths in high T stages (BWH, T2; AJCC8, T3/T4). BWH T2 included 54% fewer cases >= 2 cm than AJCC8 T3/T4. BWH had a higher specificity (0.92 vs 0.80; P<.001) and positive predictive value (24% vs 11%, P<.001) for identifying cases at risk for metastasis/death, and the C-statistic was superior for BWH (P<.001). The BWH T2 10-year cumulative incidence of metastasis/death was 37% (95% confidence interval, 21%-60%). Conclusions: BWH and AJCC 8 BCC staging both capture all metastases and deaths in the upper stages. However, BWH staging does so in half the number of cases, thus minimizing inappropriate up-staging. The risk of metastasis or death in BWH T2 BCC is sufficient to warrant surveillance for recurrence and clinical trials of adjuvant therapy.