Abstract B126: The Will Rogers phenomenon in breast cancer: The AJCC 8th Ed. and the importance of caution in the interpretation of outcomes differences for overall population and race-specific cohorts

Abstract

Abstract Purpose: To assess whether the Will Roger’s phenomenon [WRP] exists with the move from the AJCC 7th to AJCC 8th edition in Breast Cancer staging and if racial differences are manifested in the expression of the WRP. Methods: A retrospective analysis of 300 women diagnosed with breast cancer between 2007 and 2017 at an academic medical center was performed. Pearson’s square test was used to compare the proportional differences between the anatomic staging system represented by the 7th edition and the prognostic staging of the 8th edition among Caucasian [C] and African-American [AA] women. Kaplan- Meier analysis was used to estimate overall survival [OS] and disease-free survival [DFS] between the races and compared using the log-rank test. Bi and multi-variate Cox hazard regression analyses were used to identify any racial factors associated with outcomes. The SPSS v.24.0 was used for all statistical analyses. Results: Our patient cohort included 30.3% C and 69.7% AA (median age, 62 y; range 34- 92 y). Stages I, II, III, and IV accounted for 46.2%, 26.3%, 23.1%, and 4.4% of C and 28.7%, 43.1%, 24.4%, and 3.8% of AA respectively, in anatomic staging (p= 0.043). In prognostic staging, 52.8%, 18.7%, 23%, and 5.5% were C while 35%, 17.2%, 43.5%, and 4.3 % were AA, respectively (p=0.011). A total number of 41 C (45.05 %) were upstaged compared to 100 AA (47.85 %) patients. Fifteen C patients (16.49 %) and 30 AA patients (14.35 %) were down-staged. Of the remainder, 35 C (38.46 %) and 79 AA (37.79 %) patients had their stages unchanged (P=0.859). The median follow-up duration for this cohort was 58 months (range 4- 235 months). The AA patients showed better stage -by- stage 5- year OS rates using 8th edition compared to the 7th edition, suggesting a manifestation of the WRP. Among the C patients, those who were stage IIIA in the 7th edition but became stage IB in the 8th had a better prognosis than stages IIA and IIB in the 8th edition (p=0.000). For AA patients, stage IIIA, IIIB, IIIC, and IV all demonstrated better prognoses in the 8th edition when compared to the 7th edition (p=0.000). In terms of DFS, the 8th edition’s clinical staging showed complex results (p=0.176) compared to DFS estimated using the 7th’s anatomic staging system (p=0.004). For C patients, stages IA, IB, IIB, and IIIC all recorded better DFS when using the 8th edition while for AA patients, only those with stages IB and IIIC showed better DFS in the 8th edition compared to the 7th. Conclusion: Our analyses suggest that the WRP exists in the move from the AJCC 7thto the 8th edition in breast cancer staging in both C and AA patients. However, there was significant variability between the races in the extent of its manifestation. We suggest that caution needs to be exercised when results are compared across staging systems to account for the WRP in the interpretation of the data. Citation Format: Mary R Nittala, Eswar K Mundra, SatyaSeelan Packianathan, Divyang Mehta, William C Woods, Shawn Mckinney, Barbara S Craft, Srinivasan Vijayakumar. The Will Rogers phenomenon in breast cancer: The AJCC 8th Ed. and the importance of caution in the interpretation of outcomes differences for overall population and race-specific cohorts [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B126.