Postresection CA 19-9 Predicts Overall Survival in Patients With Pancreatic Cancer Treated With Adjuvant Chemoradiation: A Prospective Validation by RTOG 9704

Purpose CA 19-9 is an important tumor marker in patients with pancreatic adenocarcinoma. A secondary end point of Radiation Therapy Oncology Group trial 9704 was prospective evaluation of the ability of postresectional CA 19-9 to predict survival. Methods CA 19-9 expression was analyzed as a dichotomized variable ( < 180 v >= 180) or ( <= 90 v > 90). Cox proportional hazards models were utilized to identify the impact of CA 19-9 expression on overall survival ( OS). Actuarial estimates for OS were calculated using Kaplan-Meier methods. Results Three hundred eighty-five patients patients had assessable CA 19-9 levels. The majority had a CA 19-9 level lower than 180 or <= 90 ( n = 220 and 200, respectively), while 34% were Lewis Antigen negative and 33 ( 9%) and 53 ( 14%) patients had levels higher than 180 and higher than 90. When CA 19-9 was analyzed as a dichotomized variable, there was a significant survival difference favoring patients with CA 19-9 lower than 180 ( hazard ratio [ HR], 3.53; P < .0001). This corresponds to a 72% reduction in the risk of death for patients with a CA 19-9 lower than 180. This was also true for patients with CA 19-9 <= 90 ( HR, 3.4; P < .0001). Multivariate analyses confirmed that CA 19-9, when analyzed as both a continuous and a dichotomized variable, is a highly significant predictor of OS in patients with resected pancreatic cancer. Conclusion To our knowledge, this is the first phase III trial to perform prospective analysis of CA 19-9 levels in patients treated with adjuvant chemoradiotherapy. It definitively confirms the prognostic importance of postresectional CA 19-9 levels after surgery with curative intent in patients with pancreatic cancer.