Abstract B44: Adjusted American Joint Committee on Cancer 6th edition stage for analysis of trends in black-white disparities in non-small cell lung cancer, SEER Medicare, 2000-2011
Authors: Richards Thomas B. , Negoita Serban , McNeel Timothy S. , Holt Dylan L. , Topor Marie , Henley S Jane , White Arica , Li Jun , Li Chunyu 
Published: May 2016

Purpose: Analyses of racial disparities in survival and treatment trends may be confounded by changes over time in cancer staging systems. For Surveillance, Epidemiology, and End Results (SEER) data linked with Medicare claims, non-small cell lung cancer (NSCLC) is available with American Joint Committee on Cancer (AJCC) 3rd edition stage from 2000–2003, and with AJCC 6th edition (AJCC6) stage from 2004–2011. We wanted to maximize the number of years that AJCC6 stage was available for analysis of trends. In this study, we describe the results of our methods to assign all NSCLC cases from 2000–2011 with stage group equivalent to AJCC6, and our assessment of black-white differences by stage and year following the stage reclassification.

Methods: We focused on SEER-Medicare linked NSCLS cases, diagnosed 2000–2011, enrolled in Medicare during the month of diagnosis, and with SEER race coded as white or black. We used SEER Extent of Disease 1988 (10 digit) codes to assign AJCC6 to cases diagnosed 2000–2003, Collaborative Stage version 1 to assign AJCC6 to cases diagnosed 2004–2009, and Collaborative Stage version 2 to assign AJCC6 to cases diagnosed 2010–2011. To evaluate our adjusted AJCC6, we calculated the percentage point (pp) differences in the proportions of cases by stage and race between 2003 and 2004, and also for the 2000–2003, 2004–2009, and 2010–2011 sub-cohorts. In addition, we used SEER Joinpoint regression analysis to calculate annual percentage change (APC) by stage and race, including coincident and parallel pairwise comparisons by race. We defined statistical significance as p&lt;0.05.

Results: Our final study cohort included 156,125 white and 16,594 black NSCLC cases. Overall from 2000 to 2011, the proportion of cases by stage was: IA (12.4%), IB (11.8%), IIA (1.2%), IIB (4.5%), IIIA (9.9%), IIIB (18.0%), and IV (41.0%); the remaining 1.2% were categorized Occult Carcinoma or Stage 0. The mean difference in proportions for stages I to IV between 2003 and 2004 was 0.3 pp, but the difference by specific stage varied up to 4.1 pp. The proportion Stage IA was higher in whites than in blacks (3.1 pp in 2000–2003; 3.7 pp in 2004–2009; and 3.5 pp in 2010–2011). The proportion Stage IV was higher in blacks than in whites (2.6 pp in 2000–2003; 3.2 pp in 2004–2009; and 3.5 pp in 2010–2011). Differences in proportions between whites and blacks for Stage IIA, IIB, and Stage IIIA were less than 1 pp for each of the three time periods. Proportions by stage for whites were greater than those for blacks for Stage IA to Stage IIB, and proportions by stage for blacks exceeded those for whites for Stage IIIB and Stage IV. The predicted proportions of white and black cases diagnosed at Stage IIIA were statistically identical. Significant changes in APCs were present among whites in Stage IA (at 2004), Stage IB (at 2006 and 2009), and Stage IV (at 2004). No statistically significant changes in APCs were detected among blacks.

Conclusion: Our methods to reclassify NSCLC cases according to AJCC6 appear reasonable to support analyses that require cancer stage and race of all cohort patients diagnosed between 2000 and 2011. Some year-to-year differences are present, but they appear at most 4.1 pp between 2003 and 2004. Following the stage reclassification, our results suggest that whites were more likely to be diagnosed at a favorable stage (IA, IB, IIA, and IIB) compared with blacks, while blacks were more likely to be diagnosed at a less favorable stage (IIIB and IV) compared with whites.

Citation Format: Thomas B. Richards, Serban Negoita, Timothy S. McNeel, Dylan L. Holt, Marie Topor, S Jane Henley, Arica White, Jun Li, Chunyu Li. Adjusted American Joint Committee on Cancer 6th edition stage for analysis of trends in black-white disparities in non-small cell lung cancer, SEER Medicare, 2000-2011. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr B44.