Comparisons of directly coded SEER Summary Stage 2000 and Collaborative Staging Derived SEER Summary Stage 2000

This study assessed comparability of the directly coded Summary Stage 2000 and the Collaborative Stage (CS) Derived Summary Stage 2000 (SS2000) using 2001-2004 data from 40 population-based cancer registries in the United States that met the high quality criteria. The likelihood ratio test was employed to determine whether stage differences between 2003 (pre-CS) and 2004 (CS) were attributable to 2001-2004 linear trends, decreases in percentage of unknown stage cases, or both. Statistically significant differences in stage distribution between 2003 and 2004 were observed for 30 out of the 34 cancer sites. For 4 cancer sites, the differences were attributable to 2001-2004 linear trends of stage distribution. For 8 cancer sites, the differences were attributable to decreases in percentage of unknown stage cases alone or in combination with the temporal trends of stage distribution. For the remaining 18 cancer sites, either (1) no linear trends of stage distribution were identified or (2) the combination of the decline in cases with unknown stage plus linear trends did not explain the stage differences between 2003 and 2004. By comparing the SS2000 and CS manuals, we found differences in coding definitions for direct extension and/or lymph node involvement for all cancer sites except cancers of the breast, cervix, and cranial nervous and other nervous system. Evidence showed that the stage differences between 2003 and 2004 may be attributable in part to the implementation of the CS System for some cancer sites.