Introduction

Serum levels of the sialyated Lewis blood group antigen CA19-9 are commonly measured during the initial investigation of patients with suspected pancreatic malignancy1 and have been demonstrated to have comparable sensitivity for ampullary adenocarcinoma when compared with pancreatic adenocarcinoma.2 CA19-9 is synthesized by the gallbladder and biliary mucosa and excreted in bile and is therefore commonly elevated in benign conditions associated with cholestasis.3–5 Approximately 5% of the population have undetectable serum CA19-9 levels due to an inability to synthesize the Lewis antigen glycosyl transferase enzyme.6

Preoperative CA19-9 levels have been used as a predictor of resectability for pancreatic malignancy to guide decision making regarding optimum use of staging laparoscopy.7 Levels of >150 kU/l (or >300 kU/l in the presence of cholestasis) have been shown to identify a patient group with periampullary malignancy at greater risk of unresectability for whom the diagnostic yield from staging laparoscopy is maximized.8,9 It is well recognized that normalization of serum CA19-9 after resection for pancreatic cancer is associated with a more favorable survival outcome10–12, but only a small number of studies have investigated whether elevated preoperative CA19-9 levels in isolation may also confer significant prognostic information in periampullary cancer.2,13,14

Previous studies have suggested that elevated preoperative C-reactive protein (CRP) levels15, thrombocytosis16,17 and lymphocytopenia18,19 may also represent potential prognostic markers in resected pancreatic cancer. We have recently reported that a combination of preoperative hematological indices, the platelet–lymphocyte ratio, represents a significant prognostic index in resected pancreatic cancer.20 However, no previous studies have investigated whether this marker of systemic inflammation might provide any prognostic information in resected ampullary cancer. Similarly, the prognostic value of preoperative CA19-9 levels adjusted for cholestasis in the same patient group has not previously been investigated. The objective of this study was to determine whether preoperative CA19-9 levels and the platelet–lymphocyte ratio might represent significant prognostic indices in patients undergoing resection for ampullary adenocarcinoma and to determine whether a combination of these parameters might provide superior prognostic information.

Materials and Methods

Prospective data were collected for all patients undergoing pylorus-preserving pancreatoduodenectomy or classical Kausch–Whipple resection between January 1997 and September 2007 at the Royal Liverpool University Hospital. Patient demographics, operative details, and the histological characteristics of the resected specimen were recorded. Processing and reporting of the pathology specimens were undertaken according to the Royal College of Pathologists’ Guidelines21 using the fifth edition of the UICC TNM Classification System.22 A positive resection margin (R1) was defined as tumor involvement within 1 mm of one or more resection margins on microscopic examination. No R2 resections were identified. Details of preoperative intervention for biliary drainage and adjuvant therapy were also recorded, and survival data were obtained from hospital computer records.

The preoperative full blood count, CA19-9, and concurrent bilirubin levels were recorded where available. The normal diagnostic reference interval for serum CA19-9 used in our laboratory is <35 kU/l. Univariate survival analysis was conducted using a CA19-9 cut-off value of 150 kU/l in non-jaundiced patients and 300 kU/l in patients with CA190-9 levels recorded in the presence of cholestasis (bilirubin >35 μmol/l). These values were selected on the basis of the previously published literature investigating the role of CA19-9 in the assessment of periampullary tumor resectability.7,8 Using a number of different cut-off points, a platelet–lymphocyte ratio of 160 was found to represent the optimum stratification point at which the survival difference between two groups was maximized.

Statistical Analysis

Continuous data were described using median, inter-quartile range (IQR) and 95% confidence intervals (CI). χ 2 or Fisher’s exact tests were used for comparative analysis of categorical data. Relationships between two continuous variables were analyzed using Spearman’s rank correlation. Survival data were analyzed using log rank testing for univariate analysis and Cox proportional hazards with forward-stepwise regression for multivariate analysis (‘NR’ signifies that the upper limit of the confidence interval for median survival was not reached). Corrected log rank p values were quoted for univariate survival where continuous prognostic data were dichotomized.23 All patients who died within 30 days of surgery were excluded from survival analysis and a p value of ≤0.05 was taken to reflect significance. Statistical analysis was performed using Statview version 5 (ISAS Institute, Cary, NC, USA) and Microsoft Excel (Microsoft Office 2007).

Results

Three hundred fifty-one consecutive patients underwent pancreatoduodenectomy for pancreatic or periampullary tumors during the study period. Seventy-seven cases had histologically confirmed adenocarcinoma arising from the ampulla of Vater. Two patients (2.6%) who died within 30 days of surgery were excluded from subsequent survival analyses. There were 37 censored cases with a median follow-up time of 22.5 months. Table 1 demonstrates the demographics of the study group along with the preoperative CA19-9 and full blood count results.

Table 1 Demographics and Preoperative CA19-9/Full Blood Count Results for Resected Ampullary Adenocarcinoma Patients
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Median overall survival of the study group was 34.9 (95% CI = 25.2 to 63.8) months. The median survival times according to preoperative CA19-9 levels (using a cut-off value of ≤150 or ≤300 kU/l in jaundiced cases) and platelet–lymphocyte ratio ≤160 together with the median survival recorded for the various histological subgroups are shown in Table 2. The corresponding survival curves when stratifying by preoperative CA19-9 and platelet–lymphocyte ratio are shown in Figs. 1 and 2, respectively. No significant correlation between CA19-9 and platelet–lymphocyte ratio was identified (Spearman, rho = 0.022, p = 0.875).

Figure 1
figure 1

Kaplan–Meier cumulative survival curves for ampullary adenocarcinoma patients stratified by preoperative CA19-9 ≤150 kU/l (or ≤300 kU/l in jaundiced cases). † A cut-off value of >150 kU/l was used to define the high-risk group for CA19-9 when recorded in the absence of concurrent cholestasis (i.e., bilirubin ≤35 µmol/l) and a cut-off value of >300 kU/l was used in the presence of cholestasis (i.e., bilirubin >35 µmol/l).

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Figure 2
figure 2

Kaplan–Meier cumulative survival curves for ampullary adenocarcinoma patients stratified by preoperative platelet–lymphocyte ratio (PLR) ≤160.

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Table 2 Median Overall Survival Times (log rank) According to Preoperative CA19-9, Platelet–Lymphocyte Ratio and Histological Sub-groups in the Overall Study Group
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A further stratification index was generated for those patients where both preoperative CA19-9 and platelet–lymphocyte ratio were recorded (n = 52). If both levels were above the selected threshold values (n = 8), patients were classified as ‘high risk’ with an associated median overall survival of 10.1 (95% CI = 7.5 to 32.4) months. If either CA19-9 or PLR were elevated individually (n = 23), patients were classified as ‘intermediate risk’ with a median survival of 25.2 (95% CI = 14.1 to 47.8) months. For the remaining cases where both levels were less than the cut-off values (n = 21), patients were classified as ‘low risk’. The median overall survival time for this group was not reached but was found to be in excess of 60 months on Kaplan–Meier analysis (Fig. 3). When comparing the survival between these groups a log rank p value of less than 0.001 was obtained.

Figure 3
figure 3

Kaplan–Meier cumulative survival curves for ampullary adenocarcinoma patients according to combined CA19-9 and PLR risk stratification.

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Table 3 demonstrates that the only significant difference between the three risk groups in terms of tumor histology was resection margin status with a trend toward an increased likelihood of margin involvement in the intermediate and high-risk groups compared with the low-risk group (Fisher’s exact, p = 0.046). There was no significant difference in the proportion of patients undergoing preoperative biliary drainage when comparing the three risk groups (p = 0.674). There was no difference in survival when comparing cases who did (n = 60) or did not require preoperative biliary drainage (n = 15) in the overall patient group [median survival = 34.9 (95% CI = 19.6 to 63.8) months and 32.7 (95% CI = 12.4 to NR) months, respectively—log rank, p = 0.988]. Similarly, there was no significant difference in the proportion of patients who went on to receive adjuvant therapy (p = 0.885).

Table 3 Tumor Characteristics According to CA19-9/Platelet–Lymphocyte Ratio Risk Stratification
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The results of a multivariate survival analysis using Cox proportional hazards with forward stepwise regression are shown in Table 4. Resection margin status, tumor size, and nodal status were included alongside the preoperative CA19-9/platelet–lymphocyte ratio risk stratification. Nodal status failed to emerge as a significant variable on forward stepwise regression (p = 0.336) and was therefore omitted from the final multivariate model. Although an association between the preoperative risk stratification and likelihood of resection margin involvement was demonstrated (Table 3), the Cox analysis suggests that both were independent prognostic variables in this patient group. Tumor differentiation was not included as an additional covariate in the multivariate model due to the lack of statistical significance on univariate analysis (Table 2, p = 0.157) and the limited number of deaths that were seen (24 out of 52) in the patient group analyzed.24

Table 4 Multivariate (Cox Proportional Hazards) Survival Analysis (n = 52)
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Discussion

CA19–9 is widely used as a diagnostic tool in the preliminary investigation of suspected periampullary malignancy.25 As a prognostic tool, failure of normalization of CA19-9 levels post-resection is strongly associated with disease recurrence and poorer survival rates.10–12 Evidence also exists to suggest that pre-resection CA19-9 levels in isolation might act as a significant predictor of survival for periampullary cancer patients,2,13,14, but the prognostic value of preoperative CA19-9 levels in resected ampullary adenocarcinomas has not previously been independently investigated. Other studies have also suggested that various preoperative inflammatory and hematological parameters such as CRP15 along with the circulating platelet16,17 and lymphocyte counts18,19 confer significant prognostic information in resected pancreatic cancer. However, no studies to date have investigated whether any markers of systemic inflammation might also represent significant independent prognostic factors in resected ampullary cancer.

Chronic inflammation is both an etiological factor and physiological consequence of pancreatic carcinogenesis.26 The proinflammatory phase associated with systemic inflammation results in release of various immunological mediators such as interleukin (IL)-1, IL-3, and IL-6, which increase circulating platelet counts as a result of megakaryocyte proliferation.27,28 Preoperative thrombocytosis is commonly associated with a number of different malignancies and has been widely reported as an adverse prognostic marker in several cancers29,30 including pancreatic adenocarcinoma.16,17 Release of inhibitory mediators such as IL-10 and transforming growth factor beta 2 as part of the inflammatory response can result in reduced circulating and tumor-infiltrating lymphocyte counts.31 Pancreatic cancer has been shown to be associated with lower preoperative lymphocyte counts when compared with other gastrointestinal cancers.32 No previous studies have been published, which have sought to investigate the immunological interaction between tumor and host in the specific context of ampullary cancer.

The results from the present study indicate that an elevated preoperative CA19-9 level and platelet–lymphocyte ratio are both associated with poorer survival in patients undergoing resection for ampullary adenocarcinoma. The lack of any correlation between these two indices suggests that both markers are influenced by different aspects of ampullary tumor biology. The Kaplan–Meier analyses for each parameter (Figs. 1 and 2) demonstrate similar survival curves. However, use of a combined index incorporating both CA19-9 and platelet–lymphocyte ratio enables a low-risk patient group to be identified with a highly favorable survival outcome (>60 months), while a high-risk group can also be predicted for whom a median survival of less than 12 months is observed. This prognostic stratification was found to remain statistically significant when analyzed alongside the important histopathological tumor characteristics. Larger tumors, poor differentiation, nodal metastases, and R1 resections all exhibited the expected trend toward poorer survival on univariate analysis in keeping with previous studies.33–35

This finding has potential clinical relevance when considering which patients with resected ampullary cancer might benefit from adjuvant therapy. Although no definitive evidence exists to advocate adjuvant therapy as an optimum treatment strategy in resected ampullary cancer,36,37 the available evidence suggests that patients with less favorable histological tumor characteristics (e.g., T3/T4 tumors) tend to see more benefit from adjuvant treatment.38–41 The preoperative risk stratification described in the present study represents a potential prognostic tool that may be of use alongside tumor histology in selecting a patient group at high risk of early recurrence and poorer overall survival for whom adjuvant therapy may be of most benefit.

The majority of patients analyzed (80%) underwent intervention for biliary drainage before resection. Instrumentation of the biliary tree represents a potential source of preoperative sepsis42 and, as such, may act as a confounding factor in interpreting the survival data. Although previous studies have suggested that biliary drainage in the preoperative setting may increase the risk of early postoperative morbidity such as wound infection,43 no evidence exists to suggest that preoperative biliary stenting has any influence on operative mortality or subsequent survival after pancreatoduodenectomy. The results from the current study confirmed that the requirement for preoperative biliary drainage had no effect on postoperative survival after resection for ampullary cancer. Furthermore, when stratifying patients into the three risk groups, there was no significant difference in the proportion of cases in each group who underwent preoperative biliary stenting. This suggests that intervention for biliary drainage is unlikely to be a significant confounding factor in explaining the marked survival differences observed when comparing the three risk-stratified groups. Similarly, there was no significant difference in the proportion of patients in each risk group who went on to receive adjuvant treatment. Hence, adjuvant therapy is also unlikely to reflect a significant confounding factor when interpreting the survival data.

Conclusion

The results of the present study suggest that significant prognostic information can be obtained from routine blood results before resection for ampullary cancer. Stratification of ampullary adenocarcinoma patients according to both preoperative CA19-9 levels and platelet–lymphocyte ratio should be considered in the survival analyses of future adjuvant and neoadjuvant trials to validate these findings.