Abstract A106: Key differences in muscular index and tumor burden reveal unique biology in ethnically diverse patients with pancreatic cancer
Authors: Cameron Miles E. , Underwood Patrick W. , Gerber Michael H. , Hughes Steven J. , Judge Andrew R. , Permuth Jennifer B. , Trevino Jose G. 
Published: August 2020

Introduction: The racial disparities in pancreatic cancer (PC), while not fully appreciated, are recognized amongst PC experts. African Americans are diagnosed more frequently, present with more advanced disease, and suffer from higher mortality rates than White patients. Overall, cancer cachexia, or cancer-associated muscle wasting, greatly contributes to both morbidity and mortality. While cachexia is experienced by more than 80% of patients with PC, PC-induced cachexia and how it contributes to a disparity amongst African Americans is under investigation. African Americans with PC present with increased muscle wasting (-29%) than their White counterparts with PC (-14%). Therefore, we hypothesize that an established radiographically obtained muscular index (a psoas index) uniquely corresponds to increased disease burden in African Americans with early-stage disease.

Methods: African American and White patients with pancreatic ductal adenocarcinoma who underwent surgery at our institution between 2010 and 2017 were included in this retrospective study. A muscular index for each patient was measured from preoperative CT scans by dividing the average area of the psoas muscles at L3 by the L3 vertebral body area to normalize the measurement for patient size. Supplementary relevant clinical, pathologic, and laboratory values were used for comparison.

Results: 15 African American and 15 White surgical patients with PC were matched by gender and history of neoadjuvant therapy; age was similar in both groups (65.7 vs. 64.3, p=0.6566). Gross tumor size was similar in African Americans and Whites (2.553 vs. 3.093, p=0.3097). Tumor size, however, inversely correlated to psoas index in African Americans (r=0.4330, p=0.0077), but not in Whites (r=0.002525, p=0.8588). African Americans with lower psoas indices generally had larger tumors. Similar to tumor size, the positive lymph node ratio (LNR) inversely correlated to psoas index in African Americans (r=0.3930, p=0.0124), but not in Whites (r=0.08673, p=0.2867). LNR was significantly greater in Whites than African Americans (0.0627 vs. 0.2253, p=0.0020). Overall survival was, however, similar in both groups (15.8 vs. 14.3, p=0.7117).

Conclusion: A decreased psoas index in African American patients is associated with greater tumor size and an increased positive LNR. Notably, the most powerful outcome variable (LNR) did not correlate with psoas index in White patients even in the presence of increased nodal metastases. Most surprisingly, overall survival was similar in both patient groups. This suggests that a limited tumor burden does not provide a survival benefit for African Americans. We conclude that recognizing biologic variance among patients with ethnic diversity will allow better strategies to characterize metabolism, tumor microenvironment, and muscle architecture in PC. Together this will lead to improved overall survival.

Citation Format: Miles E. Cameron, Patrick W. Underwood, Michael H. Gerber, Steven J. Hughes, Andrew R. Judge, Jennifer B. Permuth, Jose G. Trevino. Key differences in muscular index and tumor burden reveal unique biology in ethnically diverse patients with pancreatic cancer [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr A106.