Nipun B Merchant

Vanderbilt University, Нашвилл, Michigan, United States

Are you Nipun B Merchant?

Claim your profile

Publications (114)500.43 Total impact

  • Gastroenterology 04/2015; 148(4):S-1112. DOI:10.1016/S0016-5085(15)33789-6 · 13.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background Delayed gastric emptying (DGE) is a frequent cause of morbidity, prolonged hospital stay and readmission after a pancreaticoduodenectomy (PD). We sought to evaluate predictive peri-operative factors for DGE after a PD.Methods Four hundred and sixteen consecutive patients who underwent a PD at our tertiary referral centre were identified. Univariate and multivariate (MV) logistic regression models were used to assess peri-operative factors associated with the development of clinically significant DGE and a post-operative pancreatic fistula (POPF).ResultsDGE occurred in 24% of patients (n = 98) with Grades B and C occurring at 13.5% (n = 55) and 10.5% (n = 43), respectively. Using MV regression, a body mass index (BMI) ≥35 [odds ratio (OR) = 3.19], operating room (OR) length >5.5 h (OR = 2.72) and prophylactic octreotide use (OR = 2.04) were independently associated with an increased risk of DGE. DGE patients had a significantly longer median hospital stay (12 versus 7 days), higher 90-day readmission rates (32% versus 18%) and an increased incidence of a pancreatic fistula (59% versus 27%). When controlling for POPF, only OR length >5.5 h (OR 2.73) remained significantly associated with DGE.ConclusionsDGE remains a significant cause of morbidity, increased hospital stay and readmission after PD. Our findings suggest patients with a BMI ≥35 or longer OR times have a higher risk of DGE either independently or through the development of POPF. These patients should be considered for possible enteral feeding tube placement along with limited octreotide use to decrease the potential risk and consequences of DGE.
    HPB 02/2015; 17(6). DOI:10.1111/hpb.12385 · 2.05 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: AimsRecently, we described a series of pancreatic neuroendocrine tumours (PanNETs) featuring prominent stromal fibrosis, which we called sclerosing PanNETs. The aim of this study was to examine the pathological, immunophenotypic and clinical differences between sclerosing and non-sclerosing PanNETs.Methods and resultsOne hundred and six PanNETs were identified, of which 15 (14%) were sclerosing NETs. Tissue microarrays containing 44 non-sclerosing and five sclerosing panNETs, as well as sections from 10 additional sclerosing tumours, were immunohistochemically labelled for serotonin, CDX2, CDH17, and islet 1. Sclerosing PanNETs were smaller (P = 0.045) and more likely to show an infiltrative growth pattern (P < 0.001) than non-sclerosing PanNETs. They were frequently associated with a large pancreatic duct, causing duct stenosis. Additionally, we found significantly increased expression of the small intestinal NET markers serotonin, CDX2 and CDH17 in sclerosing PanNETs (P < 0.001) as compared with non-sclerosing PanNETs. No difference in clinical outcome was found; however, more sclerosing PanNETs were stage IIB or above (P = 0.035), with lymph node metastasis being seen in three of nine sclerosing PanNETs with a tumour size of <20 mm.Conclusions Sclerosing PanNETs have distinct pathological features and biomarker expression profiles. In addition, lymph node metastasis can be present even with small sclerosing PanNETs.This article is protected by copyright. All rights reserved.
    Histopathology 10/2014; 66(2). DOI:10.1111/his.12535 · 3.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background and Objectives Two pivotal randomized controlled trials (RCTs), the Intergroup (INT-0116) and Medical Research Council Adjuvant Gastric Infusional Chemotherapy (MAGIC) trials, demonstrated a survival benefit of multimodality therapy in patients with resectable gastric cancer. The purpose of this study was to determine utilization rates of these treatment regimens in the United States and to identify factors associated with receipt of evidence-based care.Methods We performed a retrospective cohort study of patients with Stage IB–IV (M0) gastric adenocarcinoma who underwent resection from 1991 to 2009 using the linked SEER–Medicare database.ResultsOnly 19.1% of patients received post-operative chemoradiation therapy (CRT), and 1.9% received peri-operative chemotherapy; most patients underwent surgery alone (60.9%). Patients with more advanced stage, younger age, and fewer comorbidities were more likely to receive evidence-based care. We found no association between National Cancer Institute (NCI) designation and delivery of multimodality therapy. However, patients who underwent medical oncology consultation were much more likely to receive evidence-based treatment (OR 3.10, 95% CI 2.35–4.09).Conclusions Rates of peri-operative chemotherapy and post-operative CRT in patients with resected gastric cancer remain remarkably low, despite high-quality RCT evidence demonstrating their benefit. Furthermore, NCI designation does not appear to be associated with administration of evidence-based treatment. J. Surg. Oncol. © 2014 Wiley Periodicals, Inc.
    Journal of Surgical Oncology 09/2014; 110(3). DOI:10.1002/jso.23635 · 2.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: During pancreaticoduodenectomy (PD) for ductal adenocarcinoma, a frozen section (FS) neck margin is typically assessed, and if positive, additional pancreas is removed to achieve an R0 margin. We analyzed the association of this practice with improved overall survival (OS).
    Annals of Surgery 09/2014; 260(3):494-503. DOI:10.1097/SLA.0000000000000890 · 7.19 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The NCCN Guidelines for Pancreatic Adenocarcinoma discuss the diagnosis and management of adenocarcinomas of the exocrine pancreas and are intended to assist with clinical decision-making. These NCCN Guidelines Insights summarize major discussion points from the 2014 NCCN Pancreatic Adenocarcinoma Panel meeting. The panel discussion focused mainly on the management of borderline resectable and locally advanced disease. In particular, the panel discussed the definition of borderline resectable disease, role of neoadjuvant therapy in borderline disease, role of chemoradiation in locally advanced disease, and potential role of newer, more active chemotherapy regimens in both settings.
    Journal of the National Comprehensive Cancer Network: JNCCN 08/2014; 12(8):1083-93. · 4.24 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The incidence of secondary malignancies is increased in patients with malignant and premalignant conditions. Although neuroendocrine tumors (NET) are uncommon, their incidence is increasing. We evaluated the rate of additional malignancies in patients with NET. Using the Surveillance, Epidemiology, and End Results (SEER) database, we identified a cohort of patients with pancreatic NET (PNET) or gastrointestinal NET (GINET). We determined the incidence of additional cancers diagnosed either before or after the diagnosis of PNET or GINET, by comparing these rates with the general population. Using multivariable regression, we evaluated factors that increased the risk of an additional malignancy. A cohort of 9,727 NET patients was identified. A total of 3,086 additional cancers occurred in 2,508 patients (25.8 %). The most common sites of additional malignancies included colorectal (21.1 %), prostate (14.5 %), breast (13.3 %), and lung (11.6 %). Among patients with PNET, the incidence of breast, lung, uterine, lymph, and pancreatic cancers was less than expected in the general population, whereas in patients with GINET, the observed incidence of nearly all malignancies exceeded that expected. Increasing age, marital status, and localized NET were associated with increased risk. Our study shows that the incidence of additional malignancies in patients with PNET and GINET is 25.8 %. Patients with GINET are at increased risk of additional malignancies, whereas patients with PNET have a decreased risk compared with the general population. More vigilant surveillance for secondary malignancies should be performed in patients with GINET. Studies investigating potential etiologic oncogenic pathways are warranted.
    Annals of Surgical Oncology 07/2014; 21(11). DOI:10.1245/s10434-014-3774-7 · 3.94 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this multi-institutional study of patients undergoing pancreaticoduodenectomy for pancreatic adenocarcinoma, we sought to identify factors associated with perioperative transfusion requirement as well as the association between blood transfusion and perioperative and oncologic outcomes. The surgical databases across six high-volume institutions were analyzed to identify patients who underwent pancreaticoduodenectomy for pancreatic adenocarcinoma from 2005 to 2010. For statistical analyses, patients were then stratified by transfusion volume according to whether they received 0, 1-2, or > 2 units of packed red blood cells. Among 697 patients identified, 42 % required blood transfusion. Twenty-three percent received 1-2 units, and 19 % received > 2 units. Factors associated with an increased transfusion requirement included older age, heart disease, diabetes, longer operative time, higher blood loss, tumor size, and non-R0 margin status (all p < 0.05). The median disease-free survival (13.8 vs. 18.3 months, p = 0.02) and overall survival (14.0 vs. 21.0 months, p < 0.0001) durations of transfused patients were shorter than those of transfusion-free patients. Multivariate modeling identified intraoperative transfusion of > 2 units (hazard ratio, 1.92, p = 0.009) and postoperative transfusions as independent factors associated with decreased disease-free survival. This multi-institutional study represents the largest series to date analyzing the effects of perioperative blood transfusion on patient outcomes following pancreaticoduodenectomy for pancreatic adenocarcinoma. While blood transfusion was not associated with increased rate of infectious complications, allogeneic blood transfusion did confer a negative impact on disease-free and overall survival.
    Journal of Gastrointestinal Surgery 06/2014; DOI:10.1007/s11605-014-2567-4 · 2.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Papanicolaou Society of Cytopathology has developed a set of guidelines for pancreaticobiliary cytology including indications for endoscopic ultrasound (EUS) and fine-needle aspiration (FNA) biopsy, techniques for EUS-FNA, terminology and nomenclature to be used for pancreaticobiliary disease, ancillary testing and postbiopsy management. All documents are based on expertise of the authors, literature review, discussions of the draft document at national and international meetings and synthesis of online comments of the draft document. This document selectively presents the results of these discussions. This document summarizes recommendations for the clinical and imaging work-up of pancreatic and biliary tract lesions along with indications for cytologic study of these lesions. Prebrushing and FNA requirements are also discussed.
    CytoJournal 06/2014; 11(Suppl 1):1. DOI:10.4103/1742-6413.133326
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Papanicolaou Society of Cytopathology (PSC) has developed a set of guidelines for pancreatobiliary cytology including indications for endoscopic ultrasound (EUS) guided fine-needle aspiration (FNA) biopsy, techniques of EUS-FNA, terminology and nomenclature for pancreatobiliary cytology, ancillary testing and post-procedure management. All documents are based on the expertise of the authors, a review of the literature and discussions of the draft document at several national and international meetings over an 18 month period and synthesis of online comments of the draft document on the PSC web site (www.papsociety.org). This document selectively presents the results of these discussions and focuses on the follow-up and treatment options for patients after procedures performed for obtaining cytology samples for the evaluation of biliary strictures and solid and cystic masses in the pancreas. These recommendations follow the six-tiered terminology and nomenclature scheme proposed by committee III.
    CytoJournal 06/2014; 11(Suppl 1):5. DOI:10.4103/1742-6413.133356
  • Jason A Castellanos, Nipun B Merchant
    [Show abstract] [Hide abstract]
    ABSTRACT: The management of synchronous presentation of colorectal cancer and liver metastases has long been a topic of debate and discussion for surgeons due to the unique dilemma of balancing operative timing along with treatment strategy. Operative strategies for resection include staged resection with colon first approach, "reverse" staged resection with liver metastases resected first, and one-stage, or simultaneous, resection of both the primary tumor and liver metastases approach. These operative strategies can be further augmented with perioperative chemotherapy and other novel approaches that may improve resectability and patient survival. The decision on operative timing and approach, however, remains largely dependent on the surgeon's determination of disease resectability, patient fitness, and the need for neoadjuvant chemotherapy.
    06/2014; 2(8):62. DOI:10.1007/s40137-014-0062-1
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background. Hepatic endometriosis/uterus-like mass is rare and may be overlooked during hepatic cyst workups. We report a case of uterus-like mass, misdiagnosed as hepatic abscess. Case Report: A 47-year-old woman developed abdominal pain and vomiting. Infectious colitis with hepatic abscess was diagnosed, and remained antibiotic-refractory. Fine-needle aspiration and core biopsies showed benign contents. The patient presented to our institution with symptoms and normal blood work. Laparoscopic excision demonstrated a 1.4-cm cyst composed of endometrial glands (estrogen receptor+ and progesterone receptor+) and stroma (CD10+) with smooth muscle actin (SMA+), arranged in an organoid fashion. The patient, status-post hysterectomy, had no history or symptoms of endometriosis. Conclusion. This rare case illustrates the merit of considering uterus-like mass/endometriosis in the differential diagnosis of antibiotic-refractory hepatic cysts. Cyst heterogeneity may confound needle biopsy. We report the first instance of a hepatic uterus-like mass, with a review of related entities, postulated histogenesis, and important clinical associations.
    International Journal of Surgical Pathology 05/2014; 23(2). DOI:10.1177/1066896914534465 · 0.96 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The papanicolaou society of cytopathology (PSC) has developed a set of guidelines for pancreatobiliary cytology including indications for endoscopic ultrasound (EUS) guided fine-needle aspiration (FNA) biopsy, techniques of EUS-FNA, terminology and nomenclature for pancreatobiliary cytology, ancillary testing, and postprocedure management. All documents are based on the expertise of the authors, a review of the literature, discussions of the draft document at several national and international meetings over an 18 month period and synthesis of online comments of the draft document on the PSC web site [www.papsociety.org]. This document selectively presents the results of these discussions and focuses on the follow-up and treatment options for patients after procedures performed for obtaining cytology samples for the evaluation of biliary strictures and solid and cystic masses in the pancreas. These recommendations follow the six-tiered terminology and nomenclature scheme proposed by Committee III. Diagn. Cytopathol. 2014;42:363–371. © 2014 Wiley Periodicals, Inc.
    Diagnostic Cytopathology 04/2014; 42(4). DOI:10.1002/dc.23121 · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Papanicolaou Society of Cytopathology has developed a set of guidelines for pancreaticobiliary cytology including indications for endoscopic ultrasound (EUS) and fine-needle aspiration (FNA) biopsy, techniques for EUS-FNA, terminology and nomenclature to be used for pancreaticobiliary disease, ancillary testing, and post-biopsy management. All documents are based on expertise of the authors, literature review, discussions of the draft document at national and international meetings, and synthesis of online comments of the draft document. This document selectively presents the results of these discussions. This document summarizes recommendations for the clinical and imaging work-up of pancreatic and biliary tract lesions along with indications for cytologic study of these lesions. Prebrushing and FNA requirements are also discussed. Diagn. Cytopathol. 2014. © 2014 Wiley Periodicals, Inc.
    Diagnostic Cytopathology 04/2014; 42(4). DOI:10.1002/dc.23095 · 1.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Normal pancreatic epithelium progresses through various stages of pancreatic intraepithelial neoplasms (PanINs) in the development of pancreatic ductal adenocarcinoma (PDAC). Transcriptional regulation of this progression is poorly understood. In mouse, the hepatic nuclear factor 6 (Hnf6) transcription factor is expressed in ductal cells and at lower levels in acinar cells of the adult pancreas, but not in mature endocrine cells. Hnf6 is critical for terminal differentiation of the ductal epithelium during embryonic development and for pancreatic endocrine cell specification. We previously showed that, in mice, loss of Hnf6 from the pancreatic epithelium during organogenesis results in increased duct proliferation and altered duct architecture, increased periductal fibrosis and acinar-to-ductal metaplasia. Here we show that decreased expression of HNF6 is strongly correlated with increased severity of PanIN lesions in samples of human pancreata and is absent from >90% of PDAC. Mouse models in which cancer progression can be analyzed from the earliest stages that are seldom accessible in humans support a role for Hnf6 loss in progression from early- to late-stage PanIN and PDAC. In addition, gene expression analyses of human pancreatic cancer reveal decreased expression of HNF6 and its direct and indirect target genes compared with normal tissue and upregulation of genes that act in opposition to HNF6 and its targets. The negative correlation between HNF6 expression and pancreatic cancer progression suggests that HNF6 maintains pancreatic epithelial homeostasis in humans, and that its loss contributes to the progression from PanIN to ductal adenocarcinoma. Insight on the role of HNF6 in pancreatic cancer development could lead to its use as a biomarker for early detection and prognosis.Laboratory Investigation advance online publication, 17 March 2014; doi:10.1038/labinvest.2014.47.
    Laboratory Investigation 03/2014; 94(5). DOI:10.1038/labinvest.2014.47 · 3.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Secondary bile acids (BAs) such as deoxycholic acid (DCA) promote the development of several gastrointestinal malignancies, but how they mediate this effect is unclear. In this study, we offer evidence of a mechanism involving ectodomain shedding of the EGFR ligands amphiregulin (AREG) and TGF-α which rely upon the cell surface protease TACE/ADAM-17. Specifically, we show that AREG participates in DCA-induced EGFR and STAT3 signaling, cell cycle progression and tumorigenicity in human colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC). TACE and AREG, but not TGF-α, were overexpressed in both CRC and PDAC tissues compared to normal tissues. Exposure of CRC and PDAC cells to DCA resulted in co-localization of Src and TACE to the cell membrane, resulting in AREG-dependent activation of EGFR, MAPK and STAT3 signaling. Src or TACE inhibition was sufficient to attenuate DCA-induced AREG, but not TGF-α shedding. We also examined a role for the bile acid transporter TGR5 in DCA-mediated EGFR and STAT3 signaling. RNAi-mediated silencing of TGR5 or AREG inhibited DCA-induced EGFR, MAPK and STAT3 signaling, blunted cyclin D1 expression and cell cycle progression, and attenuated DCA-induced CRC or PDAC tumorigenicity. Together, our findings define an AREG-dependent signaling pathway that mediates the oncogenic effects of secondary BAs in gastrointestinal cancers, the targeting of which may enhance therapeutic responses in their treatment."
    Cancer Research 02/2014; 74(7). DOI:10.1158/0008-5472.CAN-13-2329 · 9.28 Impact Factor
  • Journal of Surgical Research 02/2014; 186(2):501. DOI:10.1016/j.jss.2013.11.158 · 2.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Context.-PAM4 is a monoclonal antibody that shows high specificity for pancreatic ductal adenocarcinoma (PDAC) and its neoplastic precursor lesions. A PAM4-based serum immunoassay is able to detect 71% of early-stage patients and 91% with advanced disease. However, approximately 20% of patients diagnosed with chronic pancreatitis (CP) are also positive for circulating PAM4 antigen. The specificity of the PAM4 antibody is critical to the interpretation of the serum-based and immunohistochemical assays for detection of PDAC. Objective.-To determine whether PAM4 can differentiate PDAC from nonneoplastic lesions of the pancreas. Design.-Tissue microarrays of PDAC (N = 43) and surgical specimens from CP (N = 32) and benign cystic lesions (N = 19) were evaluated for expression of the PAM4 biomarker, MUC1, MUC4, CEACAM5/6, and CA19-9. Results.-PAM4 and monoclonal antibodies (MAbs) to MUC1, MUC4, CEACAM5/6, and CA19-9 were each reactive with the majority of PDAC cases; however, PAM4 was the only monoclonal antibody not to react with adjacent, nonneoplastic parenchyma. Although PAM4 labeled 19% (6 of 32) of CP specimens, reactivity was restricted to pancreatic intraepithelial neoplasia associated with CP; inflamed tissues were negative in all cases. In contrast, MUC1, MUC4, CEACAM5/6, and CA19-9 were detected in 90%, 78%, 97%, and 100% of CP, respectively, with reactivity also present in nonneoplastic inflamed tissue. Conclusions.-PAM4 was the only monoclonal antibody able to differentiate PDAC (and pancreatic intraepithelial neoplasia precursor lesions) from benign, nonneoplastic tissues of the pancreas. These results suggest the use of PAM4 for evaluation of tissue specimens, and support its role as an immunoassay for detection of PDAC.
    Archives of pathology & laboratory medicine 02/2014; 138(2):220-8. DOI:10.5858/arpa.2013-0056-OA · 2.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pancreatic ductal adenocarcinoma is an aggressive malignancy with a high mortality rate. Proper determination of the extent of disease on imaging studies at the time of staging is one of the most important steps in optimal patient management. Given the variability in expertise and definition of disease extent among different practitioners as well as frequent lack of complete reporting of pertinent imaging findings at radiologic examinations, adoption of a standardized template for radiology reporting, using universally accepted and agreed on terminology for solid pancreatic neoplasms, is needed. A consensus statement describing a standardized reporting template authored by a multi-institutional group of experts in pancreatic ductal adenocarcinoma that included radiologists, gastroenterologists, and hepatopancreatobiliary surgeons was developed under the joint sponsorship of the Society of Abdominal Radiologists and the American Pancreatic Association. Adoption of this standardized imaging reporting template should improve the decision-making process for the management of patients with pancreatic ductal adenocarcinoma by providing a complete, pertinent, and accurate reporting of disease staging to optimize treatment recommendations that can be offered to the patient. Standardization can also help to facilitate research and clinical trial design by using appropriate and consistent staging by means of resectability status, thus allowing for comparison of results among different institutions.
    Gastroenterology 01/2014; 146(1):291-304.e1. DOI:10.1053/j.gastro.2013.11.004 · 13.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pancreatic ductal adenocarcinoma is an aggressive malignancy with a high mortality rate. Proper determination of the extent of disease on imaging studies at the time of staging is one of the most important steps in optimal patient management. Given the variability in expertise and definition of disease extent among different practitioners as well as frequent lack of complete reporting of pertinent imaging findings at radiologic examinations, adoption of a standardized template for radiology reporting, using universally accepted and agreed on terminology for solid pancreatic neoplasms, is needed. A consensus statement describing a standardized reporting template authored by a multi-institutional group of experts in pancreatic ductal adenocarcinoma that included radiologists, gastroenterologists, and hepatopancreatobiliary surgeons was developed under the joint sponsorship of the Society of Abdominal Radiologists and the American Pancreatic Association. Adoption of this standardized imaging reporting template should improve the decision-making process for the management of patients with pancreatic ductal adenocarcinoma by providing a complete, pertinent, and accurate reporting of disease staging to optimize treatment recommendations that can be offered to the patient. Standardization can also help to facilitate research and clinical trial design by using appropriate and consistent staging by means of resectability status, thus allowing for comparison of results among different institutions. © RSNA and the AGA Institute, 2014 Online supplemental material is available for this article.
    Radiology 01/2014; 270(1):248-60. DOI:10.1148/radiol.13131184 · 6.21 Impact Factor

Publication Stats

2k Citations
500.43 Total Impact Points

Institutions

  • 2005–2015
    • Vanderbilt University
      • • Division of Surgical Oncology
      • • Department of Surgery
      Нашвилл, Michigan, United States
  • 2012
    • University of Cincinnati
      • Department of Surgery
      Cincinnati, OH, United States
  • 2007
    • University of Maryland, Baltimore
      Baltimore, Maryland, United States
  • 2006
    • University of Alabama at Birmingham
      Birmingham, Alabama, United States
  • 2004
    • VU University Medical Center
      • Department of Surgery
      Amsterdamo, North Holland, Netherlands