A Population-Based Validation of the American Joint Committee on Cancer Melanoma Staging System

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Abstract
Purpose A major revision of the American Joint Committee on Cancer (AJCC) stages for melanoma was implemented in 2002 after its validation in multinational cohorts including patients from cancer centers and cooperative groups. This staging system has not been validated in a US population-based cohort. Patients and Methods We used 41,417 patients with primary invasive cutaneous melanoma diagnosed between 1988 and 2001 from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) cancer registry to validate the revised AJCC staging system. Survival rates computed from stage-specific Kaplan-Meier curves (time to melanoma-specific death) were compared with the survival rates from 17,600 patients in the original AJCC validation study. Results In the SEER cohort, 65% of reported melanomas were ≤ 1.00 mm in thickness and 8.7% were more than 4.00 mm compared with 39% and 10% in the AJCC cohort (P < .001), respectively. AJCC stages were able to discriminate among SEER patient groups with different prognosis. However, SEER survival rates were significantly higher than those in the AJCC study and notably so in patients with T1a lesions (≤ 1 mm without ulceration). This population-specific effect remained significant after controlling for lesion thickness in all substages except stage IIA. Conclusion Although this national population-based study validates the most recent revision of AJCC stages for melanoma, it emphasizes that survival rates are population specific and found them to be generally higher for SEER compared with AJCC patients. Population-specific survival rates should be used in study designs and decisions about patient-specific interventions.