Critical analysis of the current American Joint Committee on Cancer staging system for cutaneous melanoma and proposal of a new staging system.

Abstract

PURPOSE To critically review the accuracy of the current American Joint Committee on Cancer (AJCC) staging system for cutaneous melanoma and propose a more useful staging system. METHODS Retrospective evaluation of the published data as well as a reanalysis of the University of Alabama and Sydney Melanoma Unit (UAB/SMU) data bases (n = 4,568) for patients with primary melanoma was performed to examine specifically the impact of level of invasion and ulceration on the prognostic value of tumor thickness. In addition, an overlay graphic technique was used to compare the Kaplan-Meier survival curves of patients with local recurrences, satellites, in-transit metastases, and nodal metastases reported in the literature. RESULTS Tumor thickness and ulceration remained the most powerful prognostic indicators in patients with stage I and II disease. Level of invasion provided statistically significant prognostic information only in the subgroup of patients with tumor thickness < or = 1 mm, but the absolute 10-year survival differences were small and inconsistent (level II, 95%; level III, 85%; level IV, 89%). The best statistical fit for tumor thickness cutoffs was at 1 versus 2 versus 4 mm. The overlay graphic technique showed that patients who developed satellite lesions or local recurrence had prognoses similar to those of patients with stage III disease. The most important prognostic factor for patients with nodal metastases was number of involved nodes rather than size. CONCLUSION Our analysis showed that the current AJCC staging system has many inaccuracies that should be modified to conform to published data. On the basis of our analysis and review of the literature, we propose a new and more accurate staging system.