The Prognostic Significance of Novel Pancreas Cancer Prognostic Index in Unresectable Locally Advanced Pancreas Cancers Treated with Definitive Concurrent Chemoradiotherapy

PURPOSE: We evaluated the prognostic quality of the novel pancreas cancer prognostic index (PCPI), a combination of CA 19-9 and systemic inflammation response index (SIRI), on the outcomes of locally advanced pancreas adenocarcinoma (LAPAC) patients who received concurrent chemoradiotherapy (C-CRT). METHODS: This retrospective analysis covered 152 unresectable LAPAC patients treated from 2007 to 2019. Receiver operating characteristic (ROC) curve analysis was used to define ideal cutoff thresholds for the pretreatment CA 19-9 and SIRI measurements, individually. The associations between the PCPI groups and progression-free- (PFS) and overall survival (OS) comprised the respective primary and secondary endpoints. RESULTS: The ROC curve analysis distinguished the respective rounded optimal cutoffs at 91 U/m/L (< versus ≥90) and 1.8 (< versus ≥1.8) for CA 19-9 and SIRI, arranging the study cohort into two significantly different survival groups for each, with resultant four likely groups: Group-1: CA 19-9<90 U/m/L and SIRI<1.8, Group-2: CA 19-9<90 U/m/L but SIRI≥1.8, Group-3: CA 19-9≥90 U/m/L but SIRI<1.8, and Group-4: CA 19-9≥90 U/m/L and SIRI≥1.8. Since the PFS (P=0.79) and OS (P=0.86) estimates of the groups 2 and 3 were statistically indistinct, we merged them as one group and created the novel three-tiered PCPI: PCPI-1: CA 19-9<90 U/m/L and SIRI<1.8, PCPI-2: CA 19-9<90 U/m/L but SIRI≥1.8 or CA 19-9≥90 U/m/L but SIRI<1.8, and PCPI-3: CA 19-9≥90 U/m/L and SIRI≥1.8, respectively. Comparative analyses unveiled that the PCPI-1 and PCPI-3 groups had the respective best and worst PFS (17.0 versus 7.5 versus 4.4 months; P<0.001) and OS (26.1 versus 15.1 versus 7.4 months; P<0.001) outcomes, while the PCPI-2 group posed in between. The multivariate analysis outcomes confirmed the novel three tired PCPI’s independent prognostic significance on either of the PFS [HR: 5.38 (95% confidence interval (CI): 4.96-5.80); P<0.001)] and OS [HR: 5.67 (95% CI: 5.19-6.15); P<0.001] endpoints, separately. CONCLUSION: The new PCPI introduced here can be used as an independent and reliable prognostic indicator to divide LAPAC patients into three subgroups with discrete survival results.