Clinical and prognostic factors for melanoma of the skin using SEER registries: collaborative stage data collection system, version 1 and version 2.

BACKGROUND: The objectives of this article are to assess the completeness of the data collected on site-specific factors (SSFs) as a part of Collaborative Stage (CS) version 2 and the impact of the transition from the American Joint Committee on Cancer's (AJCC) 6th to 7th edition guidelines on stage distribution.

METHODS: Incidence data for melanomas of the skin from 18 Surveillance, Epidemiology, and End Results (SEER) registries (SEER-18) were analyzed. Percentages of unknown cases for 7 SSFs were examined, along with staging trends from 2004 to 2010 and differences in AJCC 6th and 7th edition stage distributions for 2010 cases.

RESULTS: Fewer than 10% of cases were coded as unknown for SSFs 1 (measured thickness), 2 (ulceration), and 3 (lymph node metastasis). For the remaining SSFs, 36-81% of cases were coded as unknown. Stage distributions were relatively consistent across time and between the AJCC 6th and 7th editions, with the exception of stage IA and stage INOS (not otherwise specified), for which a shift in cases was observed between the AJCC 6th and 7th edition guidelines fOR 2010 cases.

CONCLUSIONS: A shift of cases out of stage IA and into stage INOS was observed between the AJCC 6th and 7th edition guidelines for 2010 cases. This was attributed to the high number of cases coded as unknown for SSF7 (primary tumor mitotic count/rate). The percentage of cases coded as unknown varied by SSF. Data completeness presents an issue for SSFs introduced in CS version 2.