Exocrine pancreatic cancer clinical factors were related to timing of blood extraction and influenced serum concentrations of lipids

Timing of Toenail Collection and Concentrations of Metals in Pancreatic Cancer. Evidence Against Disease Progression Bias

Trace elements such as cadmium, arsenic, zinc or selenium increase or decrease risk of a wide range of human diseases. Their levels in toenails may provide a measure of mid-term intake of trace elements for studies in humans. However, in biologically and clinically aggressive diseases as pancreatic cancer, the progression of the disease could modify such concentrations and produce reverse causation bias. The aim was to analyze the influence of specific time intervals between several clinical events and the collection of toenails upon concentrations of trace elements in patients with pancreatic cancer. Subjects were 118 incident cases of pancreatic adenocarcinoma prospectively recruited in eastern Spain. Toenails were collected at cancer diagnosis, and soon thereafter interviews were conducted. Information on cancer signs and symptoms was obtained from medical records and patient interviews. Levels of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. General linear models adjusting for potential confounders were applied to analyze relations between log concentrations of trace elements and the time intervals, including the interval from first symptom of cancer to toenail collection (iST). Toenail concentrations of the 12 trace elements were weakly or not influenced by the progression of the disease or the diagnostic procedures. Concentrations of aluminum were slightly higher in subjects with a longer iST (age, sex and stage adjusted geometric means: 11.44 vs. 7.75 µg/g for iST > 120 days vs. ≤ 40 days). There was a weak inverse relation of iST with concentrations of zinc and selenium (maximum differences of about 20 and 0.08 µg/g, respectively). Conclusions: concentrations of the trace elements were weakly or not influenced by the development of the disease before toenail collection. Only concentrations of aluminum increased slightly with increasing iST, whereas levels of zinc and selenium decreased weakly. Even in an aggressive disease as pancreatic cancer, toenail concentrations of trace elements may provide a valid measure of mid-term intake of trace elements, unaffected by clinical events and disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-021-00436-2.

Influence of KRAS mutations, persistent organic pollutants, and trace elements on survival from pancreatic ductal adenocarcinoma

INTRODUCTION

Reasons why pancreatic ductal adenocarcinoma (PDAC) continues to have poor survival are only partly known. No previous studies have analyzed the combined influence of KRAS mutations, persistent organic pollutants (POPs), and trace elements upon survival in PDAC or in any other human cancer.

OBJECTIVE

To analyze the individual and combined influence of KRAS mutations, POPs, and trace elements upon survival from PDAC.

METHODS

Incident cases of PDAC (n = 185) were prospectively identified in five hospitals in Eastern Spain in 1992-1995 and interviewed face-to-face during hospital admission. KRAS mutational status was determined from tumour tissue through polymerase chain reaction and artificial restriction fragment length polymorphism. Blood and toenail samples were obtained before treatment. Serum concentrations of POPs were analyzed by high-resolution gas chromatography with electron-capture detection. Concentrations of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. Multivariable Cox proportional hazards regression was used to assess prognostic associations.

RESULTS

Patients with a KRAS mutated tumor had a 70% higher risk of early death than patients with a KRAS wild-type PDAC (hazard ratio [HR] = 1.7, p = 0.026), adjusting for age, sex, and tumor stage. KRAS mutational status was only modestly and not statistically significantly associated with survival when further adjusting by treatment or by treatment intention. The beneficial effects of treatment remained unaltered when KRAS mutational status was taken into account, and treatment did not appear to be less effective in the subgroup of patients with a KRAS mutated tumor. POPs did not materially influence survival: the adjusted HR of the highest POP tertiles was near unity for all POPs. When considering the joint effect on survival of POPs and KRAS, patients with KRAS mutated tumors had modest and nonsignificant HRs (most HRs around 1.3 to 1.4). Higher concentrations of lead, cadmium, arsenic, vanadium, and aluminium were associated with better survival. When KRAS status, POPs, and trace elements were simultaneously considered along with treatment, only the latter was statistically significantly related to survival.

CONCLUSIONS

In this study based on molecular, clinical, and environmental epidemiology, KRAS mutational status, POPs, and trace elements were not adversely related to PDAC survival when treatment was simultaneously considered; only treatment was independently related to survival. The lack of adverse prognostic effects of POPs and metals measured at the time of diagnosis provide scientific and clinical reassurance on the effects of such exposures upon survival of patients with PDAC. The weak association with KRAS mutations contributes to the scant knowledge on the clinical implications of a genetic alteration highly frequent in PDAC.

Toenail concentrations of trace elements and occupational history in pancreatic cancer

BACKGROUND

Some occupations potentially entailing exposure to cadmium, arsenic, lead, selenium, nickel, and chromium have been associated with an increased risk of exocrine pancreatic cancer (EPC), but no studies have assessed whether body concentrations of such compounds differed among subjects occupationally exposed and unexposed. No studies which found that exposure to such metals increased the risk of EPC assessed whether past occupations were the source of exposure.

OBJECTIVE

The aim was to analyse the relationship between toenail concentrations of trace elements and occupational history in EPC patients.

METHODS

The study included 114 EPC cases personally interviewed on occupational history and lifestyle factors. Occupations were coded according to the International Standard Classification of Occupations 1988. Selected occupational exposures were assessed by two industrial hygienists and with the Finnish job-exposure matrix (Finjem). Concentrations of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. Adjusted geometric means (aGMs) and 95% confidence intervals (95% CI) were calculated.

RESULTS

Patients occupationally exposed to aromatic hydrocarbon solvents (AHs) had higher concentrations of cadmium, manganese, lead, iron and vanadium. The aGM of cadmium concentrations for cases exposed to any pesticide was 0.056 μg/g [95% CI: 0.029-0.108], and, for unexposed cases, 0.023 μg/g [0.017-0.031]. Patients occupationally exposed to pesticides had higher concentrations of cadmium and manganese. Higher concentrations of vanadium, lead and arsenic were related to exposure to formaldehyde. Vanadium and lead were also associated with exposure to chlorinated hydrocarbon solvents, and arsenic was related to exposure to polycyclic aromatic hydrocarbons (PAHs).

CONCLUSIONS

Patients occupationally exposed to AHs, pesticides, chlorinated hydrocarbon solvents, formaldehyde, volatile sulphur compounds and PAHs had higher concentrations of several metals. These elements may account for some of the occupational risks previously reported for pancreatic cancer.

Methodological issues in a prospective study on plasma concentrations of persistent organic pollutants and pancreatic cancer risk within the EPIC cohort

BACKGROUND

The use of biomarkers of environmental exposure to explore new risk factors for pancreatic cancer presents clinical, logistic, and methodological challenges that are also relevant in research on other complex diseases.

OBJECTIVES

First, to summarize the main design features of a prospective case-control study -nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort- on plasma concentrations of persistent organic pollutants (POPs) and pancreatic cancer risk. And second, to assess the main methodological challenges posed by associations among characteristics and habits of study participants, fasting status, time from blood draw to cancer diagnosis, disease progression bias, basis of cancer diagnosis, and plasma concentrations of lipids and POPs. Results from etiologic analyses on POPs and pancreatic cancer risk, and other analyses, will be reported in future articles.

METHODS

Study subjects were 1533 participants (513 cases and 1020 controls matched by study centre, sex, age at blood collection, date and time of blood collection, and fasting status) enrolled between 1992 and 2000. Plasma concentrations of 22 POPs were measured by gas chromatography - triple quadrupole mass spectrometry (GC-MS/MS). To estimate the magnitude of the associations we calculated multivariate-adjusted odds ratios by unconditional logistic regression, and adjusted geometric means by General Linear Regression Models.

RESULTS

There were differences among countries in subjects' characteristics (as age, gender, smoking, lipid and POP concentrations), and in study characteristics (as time from blood collection to index date, year of last follow-up, length of follow-up, basis of cancer diagnosis, and fasting status). Adjusting for centre and time of blood collection, no factors were significantly associated with fasting status. Plasma concentrations of lipids were related to age, body mass index, fasting, country, and smoking. We detected and quantified 16 of the 22 POPs in more than 90% of individuals. All 22 POPs were detected in some participants, and the smallest number of POPs detected in one person was 15 (median, 19) with few differences by country. The highest concentrations were found for p,p'-DDE, PCBs 153 and 180 (median concentration: 3371, 1023, and 810 pg/mL, respectively). We assessed the possible occurrence of disease progression bias (DPB) in eight situations defined by lipid and POP measurements, on one hand, and by four factors: interval from blood draw to index date, tumour subsite, tumour stage, and grade of differentiation, on the other. In seven of the eight situations results supported the absence of DPB.

CONCLUSIONS

The coexistence of differences across study centres in some design features and participant characteristics is of relevance to other multicentre studies. Relationships among subjects' characteristics and among such characteristics and design features may play important roles in the forthcoming analyses on the association between plasma concentrations of POPs and pancreatic cancer risk.

Adjusting serum concentrations of organochlorine compounds by lipids and symptoms: a causal framework for the association with K-ras mutations in pancreatic cancer

In clinically aggressive diseases, patients experience pathophysiological changes that often alter concentrations of lipids and environmental lipophilic factors; such changes are related to disease signs and symptoms. The aim of the study was to compare the effects of correcting for total serum lipids (TSL) and other clinical factors on the odds of mutations in the K-ras oncogene by organochlorine compounds (OCs), in logistic models, in 103 patients with exocrine pancreatic cancer (EPC) using a causal directed acyclic graph (DAG) framework. Results and likelihood of bias were discussed in the light of possible causal scenarios. The odds of K-ras mutated EPC was associated with some TSL-corrected OCs, including p,p'-DDT (p-value: 0.008) and polychlorinated biphenyl 138 (p-trend: 0.024). When OCs were not corrected by TSL, the OR of a K-ras mutation was significant for p,p'-DDT (p-trend: 0.035). Additionally adjusting for cholestatic syndrome increased the ORs of TSL-corrected OCs. When models were adjusted by the interval from first symptom to blood extraction (ISE), the ORs increased for both TSL-corrected and uncorrected OCs. Models with TSL-corrected OCs and adjusted for cholestatic syndrome or ISE yielded the highest ORs. We show that DAGs clarify the covariates necessary to minimize bias, and demonstrate scenarios under which adjustment for TSL-corrected OCs and failure to adjust for symptoms or ISE may induce bias. Models with TSL-uncorrected OCs may be biased too, and adjusting by symptoms or ISE may not control such biases. Our findings may have implications as well for studying environmental causes of other clinically aggressive diseases.

Serum retinol binding protein-4 and neutrophil gelatinase-associated lipocalin are interrelated in pancreatic cancer patients

OBJECTIVES

Pancreatic cancer has an extremely dismal clinical course and high fatality rate. Knowing that, adipokines could regulate insulin resistance, inflammation, immunity and carcinogenesis. Accordingly, an understanding of adipokines in relation to pancreatic cancer could be useful to improve disease outcome. We aimed to determine serum retinol binding protein-4 (RBP-4) and neutophil gelatinase-associated lipocalin (NGAL) levels in pancreatic cancer patients. Moreover, we assessed their association with tumor severity and with each other.

METHODS

A total of 23 pancreatic cancer patients and 20 healthy controls were enrolled. Fifteen of the pancreatic cancer patients underwent Whipple resection and were examined before and after operation. Serum glucose, insulin, lipid profile, CA19-9, RBP-4 and NGAL were estimated by ELISA.

RESULTS

Significant elevation in serum concentrations of RBP-4 (64.4 ± 5.6 ng/ml) and NGAL (142(80-235) ng/ml) at p < 0.001 was found in pancreatic cancer patients. Both RBP-4 and NGAL were significantly lower after operation than before operation. Moreover, NGAL was elevated in advanced pathological T stage. Interestingly, RBP-4 and NGAL levels were positively correlated (r = 0.484, p = 0.05) and they are associated with some of the lipid profile parameters.

CONCLUSIONS

Elevated serum RBP-4 and NGAL are associated with pancreatic cancer. They were positively interrelated; highlighting the possible interplay between them in pancreatic cancer.

Relationships of hepatic and pancreatic biomarkers with the cholestatic syndrome and tumor stage in pancreatic cancer

We analyzed relationships of hepatic and pancreatic biomarkers with the cholestatic syndrome and tumor stage in exocrine pancreatic cancer (N = 183). Information on laboratory tests and on signs and symptoms was obtained from medical records and patient interviews. Bilirubin, aspartate aminotransferase (AST), γ-glutamyltransferase (GGT) and alkaline phosphatase were lower in tumor stage IV. The association was due to the relationship between cholestatic syndrome and earlier presentation of patients. There was no association between hepatic biomarkers and stage when adjusting by cholestatic syndrome. Relationships of hepatic and pancreatic biomarkers with pancreatic symptoms and tumor stage must be controlled in "-omics" and other studies using biomarkers.

Distribution of blood concentrations of persistent organic pollutants in a representative sample of the population of Barcelona in 2006, and comparison with levels in 2002

INTRODUCTION

POP biomonitoring programs are useful for exposure assessment, to analyze patterns, and to evaluate policies. However, population-representative surveys are scarce and heterogeneous. Reports on time trends in representative samples using the same methods are rare.

OBJECTIVES

To analyze the distribution of serum concentrations of 19 POPs in the general population of Barcelona city in 2006, and to compare it with the distribution in 2002.

METHODS

231 participants in the Barcelona Health Survey were interviewed face-to-face, gave blood, and underwent a physical exam. Density plots ("POP Geoffrey Rose curves") were used to represent the full population distribution of each compound.

RESULTS

Eight POPs were each detected in >80% of the study subjects: p,p'-DDT, p,p'-DDE, PCB congeners 118, 138, 153 and 180, HCB and β-HCH. The minimum number of POPs detected in one person was 5, and 72% of the population accumulated ≥ 10 compounds. p,p'-DDE and HCB showed the highest concentrations (median=219 and 109 ng/g lipid, respectively). Concentrations decreased by 34-56% from 2002 to 2006. The decrease was similar in women and men, and in all age groups/birth cohorts. It was larger with increasing BMI; for p,p'-DDT, HCB and β-HCH the decrease in obese individuals was 31-44 percentage points larger than in subjects with normal weight. The distribution of POP concentrations was always switched towards higher values in women than men. POP levels also differed significantly by age, body mass index, weight gain, birth place and social class, but not by parity and breastfeeding. The two younger cohorts had a higher DDT/DDE ratio than the oldest cohort.

CONCLUSION

Although human POP contamination remains common in the city of Barcelona, concentrations decreased significantly in 4years. Our approach suggests innovative ways to conceive, analyze and present results for other monitoring programs.

How useful is it clinically to analyse the K-ras mutational status for the diagnosis of exocrine pancreatic cancer? A systematic review and meta-analysis

BACKGROUND

More clinically meaningful diagnostic tests are needed in exocrine pancreatic cancer (EPC). K-ras mutations are the most frequently acquired genetic alteration in EPC. We analysed the diagnostic utility of detecting K-ras mutations through a systematic analysis of the literature.

METHODS

We searched PubMed using suitable medical subject headings and text words. Original research articles that evaluated the diagnostic accuracy of detecting K-ras mutations for diagnosis of EPC were selected. Two investigators independently extracted data from each study regarding the methodology used, the methodological quality of the study, the diagnostic accuracy reported and the authors' conclusions about clinical applicability of the test. Combined estimates for the sensitivity and specificity of K-ras were determined using bivariate meta-analysis; heterogeneity was explored using meta-regression.

RESULTS

We assessed 34 studies from 30 published articles. The research reports were prone to numerous methodological biases and often lacked vital information for assessing external validity. The sensitivity of detecting K-ras status ranged from 0% through 100%, and the specificity from 58% through 100%. Diagnostic accuracy was highest when cytohistological samples were used: sensitivity and specificity were 76·5% (66·7-84·2) and 91·8% (87·6-94·1), respectively. Studies conducted in a clinically relevant population observed lower accuracy than case-control designs (68·4% vs. 82·7%).

CONCLUSIONS

Because of the numerous methodological limitations of studies, the utility of analysing K-ras mutations for the diagnosis of EPC remains unknown. Flaws in diagnostic biomarkers with well-established biological properties, as K-ras, become even more relevant when the promises of 'personalized medicine' are pondered.

Clinical validity of detecting K-ras mutations for the diagnosis of exocrine pancreatic cancer: a prospective study in a clinically-relevant spectrum of patients

The diagnostic utility of detecting K-ras mutations for the diagnosis of exocrine pancreatic cancer (EPC) has not been properly studied, and few reports have analysed a clinically relevant spectrum of patients. The objective was to evaluate the clinical validity of detecting K-ras mutations in the diagnosis of EPC in a large sample of clinically relevant patients. We prospectively identified 374 patients in whom one of the following diagnoses was suspected at hospital admission: EPC, chronic pancreatitis, pancreatic cysts, and cancer of the extrahepatic biliary system. Mutations in the K-ras oncogene were analysed by PCR and artificial RFLP in 212 patients. The sensitivity and specificity of the K-ras mutational status for the diagnosis of EPC were 77.7% (95% CI: 69.2-84.8) and 78.0% (68.1-86.0), respectively. The diagnostic accuracy was hardly modified by sex and age. In patients with either mutated K-ras or CEA > 5 ng/ml, the sensitivity and specificity were 81.0% (72.9-87.6) and 62.6% (72.9-87.6), respectively. In patients with mutated K-ras and CEA > 5 ng/ml the sensitivity was markedly reduced. In comparisons with a variety of non-EPC patient groups sensitivity and specificity were both always greater than 75%. In this clinically relevant sample of patients the sensitivity and specificity of K-ras mutations were not sufficiently high for independent diagnostic use. However, it seems premature to rule out the utility of K-ras analysis in conjunction with other genetic and 'omics' technologies.

Methodological deficits in diagnostic research using '-omics' technologies: evaluation of the QUADOMICS tool and quality of recently published studies

Background

QUADOMICS is an adaptation of QUADAS (a quality assessment tool for use in systematic reviews of diagnostic accuracy studies), which takes into account the particular challenges presented by ‘-omics’ based technologies. Our primary objective was to evaluate the applicability and consistency of QUADOMICS. Subsequently we evaluated and describe the methodological quality of a sample of recently published studies using the tool.

Methodology/Principal Findings

45‘-omics’- based diagnostic studies were identified by systematic search of Pubmed using suitable MeSH terms (“Genomics”, “Sensitivity and specificity”, “Diagnosis”). Three investigators independently assessed the quality of the articles using QUADOMICS and met to compare observations and generate a consensus. Consistency and applicability was assessed by comparing each reviewer's original rating with the consensus. Methodological quality was described using the consensus rating. Agreement was above 80% for all three reviewers. Four items presented difficulties with application, mostly due to the lack of a clearly defined gold standard. Methodological quality of our sample was poor; studies met roughly half of the applied criteria (mean ± sd, 54.7±18.4%). Few studies were carried out in a population that mirrored the clinical situation in which the test would be used in practice, (6, 13.3%); none described patient recruitment sufficiently; and less than half described clinical and physiological factors that might influence the biomarker profile (20, 44.4%).

Conclusions

The QUADOMICS tool can consistently be applied to diagnostic ‘-omics’ studies presently published in biomedical journals. A substantial proportion of reports in this research field fail to address design issues that are fundamental to make inferences relevant for patient care.

The relative influence of diet and serum concentrations of organochlorine compounds on K-ras mutations in exocrine pancreatic cancer

BACKGROUND

In exocrine pancreatic cancer (EPC) mechanistic relationships may exist among some organochlorine compounds (OCs) and mutations in the K-ras oncogene, as well as among the latter and dietary factors.

OBJECTIVE

To analyze (1) the relationship between food intake and serum concentrations of OCs in EPC patients and (2) the relative influence of food and OCs on the frequency of K-ras mutations in EPC.

PATIENTS AND METHODS

Incident cases of EPC were prospectively identified, and interviewed face-to-face during hospital admission (N=135 patients with data on OCs and diet, and N=97 with additional information on K-ras status). OCs were measured by high-resolution gas chromatography with electron-capture detection.

RESULTS

Consumption of milk and other dairy products was positively associated with concentrations of p,p'-DDT, PCB 138 and PCB 153 (log-transformed betas=0.652, 0.588 and 0.317, respectively; all p<0.05). When adjusted by OCs, dairy products were no longer associated with K-ras. By contrast, after adjusting by consumption of dairy products, patients with the highest concentrations of p,p'-DDT and some PCBs remained more likely to have a K-ras-mutated EPC than patients with lower concentrations (OR for upper tertile of PCB 138=5.5, 95% CI: 1.3-23.4).

CONCLUSIONS

Dairy products were a source of OCs. The association between dairy products and K-ras mutations was not independent of OCs. By contrast, the association between OCs and K-ras was not confounded by dairy products. OCs may be more likely to contribute to the occurrence of K-ras mutations than nutrients contained in dairy products.

Do metabolic alterations serve as biochemical markers in the diagnosis of malignant biliary obstruction? An observational study

OBJECTIVES

The aim of this study was to investigate the changes in serum lipid profiles in biliary obstruction associated with benign and malignant conditions and to find whether they can be used as adjunctive biochemical tumor markers in the differential diagnosis.

METHODS

One hundred and twenty patients (60 malignant, 60 benign) who underwent endoscopic retrograde cholangiopancreatography with the clinical picture of intrahepatic and extrahepatic cholestasis were reviewed in the period from January to July 2008.

RESULTS

In the malignant group, significantly higher cholesterol (P<0.001), low-density lipoprotein (P<0.001), and triglycerides (P<0.001) were observed, whereas high-density lipoprotein (P<0.001) levels were lower. The receiver operating characteristic analysis showed that high-density lipoprotein 19.5 mg/dl or less [sensitivity: 88.3%, specificity: 83.3%, area under the curve: 0.906 (0.851-0.961), P<0.001] and total to -high-density lipoprotein cholesterol ratio at least 17.7 [sensitivity: 80.0%, specificity: 93.1%, area under the curve: 0.921 (0.871-0.971)] were strong predictors of malignant biliary obstruction.

CONCLUSION

Serum lipid profile may be used as an adjunctive marker to identify malignant causes of the obstructive jaundice.

In pancreatic ductal adenocarcinoma blood concentrations of some organochlorine compounds and coffee intake are independently associated with KRAS mutations

While KRAS activation is a fundamental initiating event in the aetiopathogenesis of pancreatic ductal adenocarcinoma (PDA), environmental factors influencing the occurrence and persistence of KRAS mutations remain largely unknown. The objective was to test the hypothesis that in PDA there are aetiopathogenic relationships among concentrations of some organochlorine compounds (OCs) and the mutational status of the KRAS oncogene, as well as among the latter and coffee intake. Incident cases of PDA were interviewed and had blood drawn at hospital admission (N = 103). OCs were measured by high-resolution gas chromatography with electron capture detection. Cases whose tumours harboured a KRAS mutation had higher concentrations of p,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-dichlorodiphenyldichloroethene (DDE) and polychlorinated biphenyls (PCBs) 138, 153 and 180 than cases with wild-type KRAS, but differences were statistically significant only for p,p'-DDT and PCBs 138 and 153. The association between coffee intake and KRAS mutations remained significant (P-trend < 0.015) when most OCs where accounted for. When p,p'-DDT, PCB 153, coffee and alcohol intake were included in the same model, all were associated with KRAS (P = 0.042, 0.007, 0.016 and 0.025, respectively). p,p'-DDT, p,p'-DDE and PCB 138 were significantly associated with the two most prevalent KRAS mutations (Val and Asp). OCs and coffee may have independent roles in the aetiopathogenesis of PDA through modulation of KRAS activation, acquisition or persistence, plausibly through non-genotoxic or epigenetic mechanisms. Given that KRAS mutations are the most frequent abnormality of oncogenes in human cancers, and the lifelong accumulation of OCs in humans, refutation or replication of the findings is required before any implications are assessed.

Correcting serum concentrations of organochlorine compounds by lipids: alternatives to the organochlorine/total lipids ratio

INTRODUCTION

When studying the effects of organochlorine compounds (OCs) on human health it is common to correct serum concentrations of OC by total lipids (TL). However, the relationship between serum OCs and serum TL is far from established in many diseases, including several cancers. Our aim was to analyze the relationship between serum OC and TL in patients with pancreatic ductal adenocarcinoma (PDA), and to explore several alternatives to perform the OC lipid correction.

METHODS

Incident cases of PDA were interviewed and had blood drawn soon around hospital admission (n=144). Serum concentrations of OCs were analysed by high-resolution gas chromatography with electron-capture detection.

RESULTS

Most patients with high TL had moderate or low concentrations of OCs. By contrast, the variability of OC values among patients with normal TL was large. Correlations were of a similar magnitude between OC and TL and between OC and total cholesterol; while these correlations were weak (all Spearman's rho<0.3 and R(2)<0.11), no OC were significantly correlated with triglycerides. Although all alternatives to the OC/TL linear ratio were statistically significant for at least one OC, their R(2) was always below 10%.

CONCLUSIONS

In patients with severe diseases as PDA, linear correction of OC by TL as commonly performed in epidemiologic studies may be inappropriate. Results contribute to the scant literature on the rationale to correct serum concentrations of OC by lipids. They suggest that it is unwarranted to routinely correct OC by TL, offer ways to assess such need, and present alternatives as no TL correction, correction by total cholesterol only or use of different statistical models.

Differences in serum concentrations of organochlorine compounds by occupational social class in pancreatic cancer

BACKGROUND

The relationships between social factors and body concentrations of environmental chemical agents are unknown in many human populations. Some chemical compounds may play an etiopathogenic role in pancreatic cancer.

OBJECTIVE

To analyze the relationships between occupational social class and serum concentrations of seven selected organochlorine compounds (OCs) in exocrine pancreatic cancer: dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethene (p,p'-DDE), 3 polychlorinated biphenyls (PCBs), hexachlorobenzene, and beta-hexachlorocyclohexane.

METHODS

Incident cases of exocrine pancreatic cancer were prospectively identified, and interviewed face-to-face during hospital admission (n=135). Serum concentrations of OCs were analyzed by high-resolution gas chromatography with electron-capture detection. Social class was classified according to occupation.

RESULTS

Multivariate-adjusted concentrations of all seven compounds were higher in occupational social classes IV-V (the less affluent) than in classes I-II; they were higher as well in class III than in classes I-II for four compounds. Concentrations of six OCs were higher in manual workers than in non-manual workers (p<0.05 for PCBs). Social class explained statistically between 3.7% and 5.7% of the variability in concentrations of PCBs, and 2% or less variability in the other OCs.

CONCLUSIONS

Concentrations of most OCs were higher in the less affluent occupational social classes. In pancreatic cancer the putative causal role of these persistent organic pollutants may not be independent of social class. There is a need to integrate evidence on the contribution of different social processes and environmental chemical exposures to the etiology of pancreatic and other cancers.

Timing of blood extraction in epidemiologic and proteomic studies: results and proposals from the PANKRAS II Study

There are no consensus guidelines or standards for epidemiologic and '-omics' studies using blood biomarkers on how to report the timing of extraction of blood samples. However, disease-induced changes in blood concentrations of exogenous and endogenous compounds may bias studies. The aim of the present report is to describe the timing of blood collection with respect to a variety of relevant clinical events in the PANKRAS II Study, and to suggest ways to display graphically the quantitative information. Subjects were 167 incident cases of exocrine pancreatic cancer prospectively recruited in five teaching hospitals in eastern Spain. Over 80% of patients had blood extracted during the first 6 months since onset of cancer symptoms, and 82% within the first month of admission to a study hospital. Over 80% of cases had blood drawn after an ultrasound, a CT scan or an ERCP, 25% after a laparotomy, and 37% after treatment onset. All three intervals from blood extraction to diagnosis, to treatment onset and to interview had a median of 0 days, and 88% of cases had blood drawn within 2 weeks of diagnosis. Over 72% of cases had concentrations of total lipids in the medium, normal range. Results suggest ways to report intervals involving blood biomarkers and may contribute to develop consensus guidelines and standards on the collection of blood samples in epidemiologic and '-omics' research.