Low HDL-Cholesterol is Associated with Malignant Intraductal Papillary Mucinous Neoplasms: A Multicenter Study

Background: Intraductal papillary mucinous neoplasms (IPMNs) has the potential of malignant transformation. Previous studies showed that HDL-c was related to risk of cancer. In this study, we showed the association between HDL-c and the incidence of malignancy in IPMNs. Material and methods: 226 patients with histologically proven IPMNs who underwent surgery were included in the present study. 151 patients were assigned to training group andother 75 patients was set as a validation. Patients’ demographic information, clinical data, and pathological features were obtained from medical records. Those with high grade dysplasia and invasive carcinoma were dened as malignant IPMNs. Logistic regression analyses were used to show the association between HDL-cand malignant IPMNs. Receiver operating characteristic (ROC) curves were performed to show the predictive performance. Results: Prevalence of low HDL-c in patients with malignant IPMNs was higher than those with non-malignant IPMNs (p < 0.01) both in training group and validation group. Prevalence of malignant IPMNs was decreased with the increase of HDL-c both in all IPMNs and Branch-Duct IPMNs (BD-IPMNs).Logistic analysis showed that low HDL-c was associated with malignant IPMNs (OR =20.56, 95% CI:2.58 - 163.64) in all IPMNs and BD-IPMNs (OR = 17.6, 95%CI: 1.16-268.46).The predictive performance of mural nodule plus low HDL-c was higher than that of mural nodule alone or mural nodule plus cyst size in identifying malignant BD-IPMNs. Conclusion: HDL-c may be a potential biomarker for identifying malignant IPMNs. Moreover, HDL-c may improve the predictive ability of malignancy in BD-IPMNs. such as lifestyle and diet habits. Finally, HDL-associated proteins and enzymes were not easily affected by covariates. We did not observed the association between malignant IPMNs and them. Our study is an exploration. In conclusion, our data shows that low HDL-c is associated with malignant IPMNs. Low HDL-c may be a potential biomarker for identifying malignant IPMNs. Moreover, HDL-c may improve the predictive ability of malignancy in BD-IPMNs. Prospective study is needed to evaluate the role of HDL-c in malignancy of IPMNs.


Introduction
Intraductal papillary mucinous neoplasms (IPMNs) are common cystic neoplasms of pancreas. IPMNs has the potential of malignant transformation. The neoplastic transformation may culminate in invasive carcinoma in some patients [1], and IPMNs have the potential to progress from low-grade dysplasia to invasive carcinoma over the time [2,3]. The incidence of high-grade dysplasia or pancreatic cancer in IPMNs was 42% [4]. IPMNs include three types considering the degree of involvement of the pancreatic ductal system: main duct (MD), branch duct (BD), and mixed type (features of MD and BD). Surgical intervention is recommended for MD IPMNs and mixed IPMNs because the high risk of malignancy [5].Management of BD-IPMNs remains challenging.
High-risk stigmata and worrisome features have been applied to identify high-grade dysplasia or invasive carcinoma [6], such as diameter of main pancreatic duct (MPD) and enhanced mural nodule > 5 mm. Several studies also have shown the elevated tumor biomarkers was associated with invasive carcinoma in IPMNs, including carcinoembryonic antigen (CEA) and serum carbohydrate antigen 19 − 9 (CA19-9) [5]. However, those approaches are still not satis ed because of inadequate sensitivity and speci city [6]. There are inconsistencies among published guidelines [7]. In addition, some efforts were also made to predict malignant IPMN by using novel approach, such as extracellular vesicle [8]. However, few biomarkers have been used to identify malignancy in BD-IPMNs.
Cholesterol plays a critical role in cancer progression by enhancing cell proliferation, migration, and invasion [9]. High-density lipoprotein (HDL) is the main lipoprotein cholesterol transporter to the major steroidogenic organs [10,11]. HDL protects against cancer development through its pleiotropic properties, including anti-oxidation and modulating cytokine production, and by blocking apoptosis, cell-growth stimulation and migration [12,13]. HDL potentially antagonizing two main hallmarks of cancer progression via its potent antioxidant and anti-in ammatory properties [14,15]. The association between high density lipoprotein-cholesterol (HDL-c) and cancer risk was also reported, including breast cancer [11,16], prostate and ovarian cancer [11]. In addition, similar correlation was also found between HDL-c levels and risk of gastrointestinal cancer, such as liver cancer [17,18], biliary tract cancer [19, 20] and pancreatic cancer [11,21,22]. However, to the best of our knowledge, the role of HDL-c in IPMNs has not been investigated. In the present multicenter study we observed the association between HDL-c and the incidence of malignancy in IPMNs, particularly to BD-IPMN.

Materials And Methods
Patients 226 patients with biopsy proven IPMN who underwent surgery during 2011-2020 in three centers were included in the present study after excluding those patients with data missing or receiving chemotherapy/radiotherapy. 151 patients in center 1 and center 2 were set as training group. Other 75 patients in center 3 was considered as validation group. Patients' demographic information, clinical data, and pathological features were obtained from medical records. We collected the data of preoperative symptoms (such as abdominal symptoms and overt jaundice), serum carbohydrate antigen 19-9 (CA19-9) level, serum carcinoembryonic antigen (CEA) levels, HDL-c, low density lipid (LDL), triglyceride (TG) and total cholesterol (TC). The medical history of pancreatitis and diabetes were collected. Fasting plasma glucose levels and 2-h plasma glucose levels were determined within one week before the operation. The diabetes mellitus (DM) was de ned according to plasma glucose levels and history of DM. Imaging information was obtained from PACS. This retrospective study was approved by the Institutional Ethic Review Board of the First A liated Hospital, Zhejiang University School of Medicine. Informed consent was waived.

Imaging analysis
All patients underwent magnetic resonance imaging (MRI) examinations. T1 weighted imaging (T1WI), T2WI, MRCP and contrast-enhanced imaging were obtained. The following imaging ndings were recorded: MPD diameter, enhanced mural nodule, cyst location, cyst size and the communication with MPD.

Malignant IPMN
IPMN was classi ed into three types considering the degree of involvement of the pancreatic ductal system: MD, BD, and mixed type. IPMN was classi ed into low-intermediate dysplasia, high-grade dysplasia, and invasive adenocarcinoma. Malignant IPMNs were de ned as those with high grade dysplasia and associated invasive carcinoma.
Statistical analysis HDL-c was divided into two groups: < 0.7 mmol/L and ≥ 0.7 mmol/L. The two-tailed t tests or Mann-Whitney U-test were used to compare the variables. Univariable and multivariable logistic regression analyses were used to show the association between low HDL-c and malignant IPMNs. The results were additionally adjusted with diabetes and pancreatitis. Receiver operating characteristic (ROC) curves were performed to show the performance of mural nodule plus low HDL-c in evaluating malignant IPMN. P values less than 0.05 were considered as statistically signi cant.

Results
The clinical data of patients The clinical data of patients in training group and validation group is shown in Table 1. There were 47 patients (31.1%) with malignant IPMN in training group and 19 malignant IPMN (25.3%) in validation group. Prevalence of low HDL-c in patients with malignant IPMN was higher than those with non-malignant IPMN (p < 0.01) both in training group and validation group. 77.8% patients with low HDL-c had malignant IPMNs. Similar data was observed in validation group (75.0%). The prevalence of malignant IPMN was decreased with the increase of HDL-c both in all IPMNs and BD-IPMNs (Fig.1).

The association between low HDL-c and malignant IPMNs
Univariable and multivariable logistic regression were used to identify the associated factors for malignant IPMNs (Table 2). Compared with MD involved IPMN, BD IPMN had a lower risk for malignancy (OR = 0.13, 95% CI: 0.05 -0.34). However, this association was disappeared when adjusting to high risk stigmata (diameter of main pancreatic duct and mural nodule). Low HDL-c was associated with the presence of malignant IPMNs (OR = 8.93, 95% CI: 1.78 -44.80), and such association was remained after adjusting for diabetes, pancreatitis and serum LDL level (OR = 20.56, 95% CI: 2.58 -163.64). Similar trend was found in validation group (OR = 6.66, 95%CI: 1.08 -41.06).

Discussion
The diagnosis and clinical management strategies of them still remains controversial currently because of the absence of factors that predict malignancy clearly [23]. Tumor biomarkers, such as CEA and CA19-9, were also used to predict the malignancy [5]. Our study demonstrated a reverse association between HDL-c and IPMN. Low HDL-c in malignant IPMN were signi cantly higher than non-malignant IPMNs. Multivariable logistic analysis further showed that low HDL-c was associated with occurrence of malignant IPMN. In addition, the combination of mural nodule and low HDL-c showed higher performance than mural nodule alone or combination of mural nodule plus cyst size in predicting malignant BD-IPMNs. Low HDL-c may be a potential biomarkers for malignant IPMNs.
An inverse relationship between serum total cholesterol levels and cancer risk has been reported [24][25][26]. Moreover, the associations between HDL-c and cancer risk, disease free survival (DFS) or overall survival (OS) have been reported in many malignancies [11,[16][17][18][19][20][21][22]27]. Low HDL-C levels were associated with high TNM stage and occurrence of distant metastasis [28]. It is noteworthy that, in several studies, the HDL-c had shown the reverse correlation with the gastrointestinal cancer. The randomized controlled intervention studies showed [21] that the inverse associations of HDL-c with pancreatic cancer were not materially affected by other lipids, and the inverse association was unchanged after exclusion of the rst 3 years of follow-up. Michalaki et.al [22] reported that serum HDL concentration was signi cantly lower in pancreatic cancer patients than in the controls. Serum apolipoprotein A-II, transthyretin, and apolipoprotein A-I were also decreased at least 2-fold in pancreatic cancer compared with the control group [29].HDL-c levels were inversely associated with the risk of developing liver cancer [17], and pre-operative HDL-c levels was associated with the risk of cancer recurrence [18]. Patients in the lowest quintile of HDL-c (< 30 mg/dL) had a 11.6-fold higher risk of gallbladder cancer and a 16.8-fold higher risk of bile duct cancer, relative to the reference group [20]. Moreover, alteration for HDL levels may be a therapeutic strategy for cancer [30]. However, the association between HDL-c and malignant IPMNs has not been clari ed.
Interestingly, our data showed that low serum HDL-c was an independent risk factor for malignancy in IPMN both in training population and validation population even after adjustment for confounding factors. In addition, the diagnostic performance of mural nodule plus MPD diameter and low HDL-c was similar with mural nodule plus MPD diameter and CA19-9. Management of BD-IPMNs remains challenging[31]. Few biomarkers have been used to identify malignancy in BD-IPMNs. Our data showed that low serum HDL-c improved the diagnostic performance of mural nodule in predicting malignant BD IPMN. The AUC was increased from 0.71 to 0.81. Interestingly, we also observed a reverse association between low HDL-c (< 0.8 mmol/L) and grade 3 pancreatic neuroendocrine neoplasms (PNENs) (n = 197, OR = 2.37, 95%CI: 1.001-5.62, data not shown). These data further support that low HDL-c is associated with malignant pancreatic diseases. However, con icting evidence was also reported between HDL and cancer incidence or mortality because this association may be tumor-type-dependent [30]. Anyway, there is increasing evidence that supports this association [30]. Our study has several limitations. First, the sample size was relatively small, especially for number of malignant IPMNs or carcinoma in BD-IPMNs. Second, it would be better to perform a longitudinal study to show the baseline serum HDL-c and developing malignant IPMNs. Third, whether low HDL-c level is a consequential or causal factor in malignant IPMNs need further exploration. Fourth, some confounding factors were not considered, such as lifestyle and diet habits. Finally, HDL-associated proteins and enzymes were not easily affected by covariates. We did not observed the association between malignant IPMNs and them. Our study is an exploration.
In conclusion, our data shows that low HDL-c is associated with malignant IPMNs. Low HDL-c may be a potential biomarker for identifying malignant IPMNs. Moreover, HDL-c may improve the predictive ability of malignancy in BD-IPMNs. Prospective study is needed to evaluate the role of HDL-c in malignancy of IPMNs.     The receiver operating characteristic (ROC) curves of variables in predicting malignantintraductal papillary mucinous neoplasms (IPMNs). A: mural nodule plus MPD diameter and Ca19-9 or low HDL-c in predicting malignant IPMN. B: mural nodule alone, mural nodule plus cyst size, and mural nodule plus low HDL-c in predicting malignant branch duct IPMNs (BD-IPMNs).