Pancreatic ductal adenocarcinoma (PDAC) remains one of the solid malignancies with a poor prognosis despite some improvements gained over the course of centuries past. This is because the majority of patients were diagnosed with a locally advanced or metastatic disease.
1 One key factor for adequate treatment is reliable, detailed knowledge of the actual extent of disease and the patient’s condition at initial diagnosis. To date, this was based mainly on the radiographic description of vascular involvement by the tumour and the presence of distant metastases. Recently, factors reflecting tumour biology, such as CA19-9 serum concentration and suspected lymphadenopathy as well as patients’ condition, were added to the clinical estimation of disease stage and outcome.
2–5 However, the body’s inflammatory response to the presence of a malignancy was frequently neglected, despite that it showed a significant impact on outcome in PDAC.
6–10
Among a wide range of inflammatory mediators, cytokines stimulate tumour development at different stages from tumourigenesis to dissemination. In addition, they affect treatment response and are associated with rapid deterioration and a dismal prognosis.
11–14 In clinical practice, this is simply reflected by the production of acute phase proteins, such as C-reactive protein (CRP) and the increase of circulating blood leucocytes.
15,16 The link between systemic inflammation and tumour behaviour implies the identification of clinically available surrogate markers to determine the extent of the disease.
17–19
Discussion
The present study assessed the preoperative conducted PI applicability for survival prognostication in patients with PDAC undergoing resection. The PI was found to be a strong independent prognostic factor for survival that was superior to other prognostic factors, such as tumour grade, stage, and CA 19-9. In this analysis, of all concomitant factors that interact with the immune and inflammation cascade, the presence of a bile stent was the only factor that influenced the PI’s strength for survival prognostication.
21–31
Prognosis estimation in PDAC patients undergoing resection mainly relies on postoperative available factors. The AJCC/UICC tumour stage, which becomes available only after histopathological reworking, provides the basis for subsequent treatment decisions.
2,32 To date, postoperative survival is not routinely estimated before treatment of PDAC. CA 19-9 is the only biomarker available for prognostication, yet the high specificity limits its utility and definitive applicability with respect to treatment response can only be determined during treatment course in terms of marker decrease.
34 In addition, we show that the PI proves highly significant as an independent prognostic factor in contrast to CA 19-9. Consequently, the investigation of screening biomarkers that can be reliantly applied before surgery is of the utmost importance.
Cancer-related inflammation is a hallmark of cancer.
35 Next to tumour proliferation, maintenance and dissemination, it promotes angiogenesis, disarrangement of adaptive immunity as well as impaired chemotherapy response.
36 Accordingly, specific scores have been established on the basis of inflammatory markers that have been validated as prognosticators of therapy response and outcome in patients with solid malignancies.
6,7,9,17,18,20,37–41 However, some of these prognostic scores require extended analysis of differential blood cell count, which is not routinely measured in patients with primary PDAC undergoing resection.
6–8,10,18,40,41 The PI involves CRP and WBC as prognostic biomarkers. CRP has demonstrated superior prognostic impact in survival estimation of cancer patients compared with WBC components and albumin.
40,42 High CRP levels reflect the risk of cancer incidence and cancer-associated death.
42,43 The PI and the (modified) Glasgow Prognostic Score, made up of CRP and albumin, are powerful prognostic tools in a variety of cancers compared with the neutrophil–lymphocyte ratio (NLR), the platelet-lymphocyte ratio (PLR), and the prognostic nutritional index (PNI).
40,41 With regards to PDAC, neutrophilia in particular has been associated with pro-cancer effects.
44 In the present analysis, a strong correlation between WBC and tumour stage was found, with higher WBC counts in patients with nodal-positive disease. These findings reflect the utility of leucocytes as valid biomarkers for patients with PDAC undergoing resection. Consequently, the combination of both markers, CRP and WBC, might most reliably reflect the inflammatory status of the patients allocated to surgery. Another advantage of the PI is its cost effectiveness and availability during initial routine blood tests.
20 In contrast, scores, such as the neutrophil–lymphocyte ratio (NLR), the platelet-lymphocyte ratio (PLR), and the prognostic nutritional index (PNI), use parameters that need to be obtained by differential blood tests.
Previous analyses of PDAC specimens after neoadjuvant treatment have yielded conflicting results regarding the state of cancer-related inflammation. However, neoadjuvant treatment seems to induce an altered immune response that influences survival.
28,30,31,45 We show that the PI’s prognostic strength is not impaired by neoadjuvant therapy. Of note, one might speculate to exclude patients with borderline resectable or locally advanced PDAC from this analysis due to the different treatment setting; however, in this study, we wanted to test the influence of concomitant factors (and neoadjuvant treatment as such) on the PI’s strength on survival prognostication. Still, in a subgroup analysis with primary resectable patients only (
n = 307), the PI persisted as solid and strong independent factor for survival. Next to chemotherapy, further concomitant factors such as age, diabetes, smoking and high bilirubin levels common in the PDAC patient population, have been shown to interact with the immune- and inflammation cascade and thus might influence the PI’s prognostic strength.
21–31 We demonstrate that the only factor that influences the PI’s strength for survival prognostication is the presence of a bile stent. In contrast to risk factors that are chronically present (age, diabetes, smoking), preoperative introduction of a bile stent fosters (incipient) cholangitis. Although patients who had a bile stent did not suffer from higher PI levels (compared with those without bile stent), bacterial overgrowth caused by the intervention maintains (chronic) inflammation, which on the one hand might not impair CRP and WBC levels but on the other hand hampers physical reserves and thus postoperative survival.
46,47 However, despite the presence of PDAC-specific risk factors, progressive tumour mass (CA 19-9) as well as tumour stage, the PI is a reliable tool for preoperative survival prognostication in PDAC patients undergoing resection.
To our knowledge, this is the first study to assess the PI’s clinical utility for survival estimation in a selected cohort of patients with PDAC undergoing resection. The results indicate that the PI is a reliable tool in predicting disease-specific survival prior to surgery. In addition, the PI may perform better than other scores for survival prognostication, most likely due to the combination of CRP and WBC and its robustness against other concomitant factors. Nonetheless, this study is of retrospective nature and reflects an unicentre experience. Thus, the above findings require validation by a prospective, multicentre protocol.
In conclusion, the determination of the PI as a prognostic biomarker for systemic inflammatory activity offers an opportunity to identify patients at risk for poor survival prior to surgery. However, prospective multicentre studies are required to prove this concept.
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