Advances in the management of pancreatic cystic neoplasms

Progress of single-cell RNA sequencing combined with spatial transcriptomics in tumour microenvironment and treatment of pancreatic cancer

In recent years, single-cell analyses have revealed the heterogeneity of the tumour microenvironment (TME) at the genomic, transcriptomic, and proteomic levels, further improving our understanding of the mechanisms of tumour development. Single-cell RNA sequencing (scRNA-seq) technology allow analysis of the transcriptome at the single-cell level and have unprecedented potential for exploration of the characteristics involved in tumour development and progression. These techniques allow analysis of transcript sequences at higher resolution, thereby increasing our understanding of the diversity of cells found in the tumour microenvironment and how these cells interact in complex tumour tissue. Although scRNA-seq has emerged as an important tool for studying the tumour microenvironment in recent years, it cannot be used to analyse spatial information for cells. In this regard, spatial transcriptomics (ST) approaches allow researchers to understand the functions of individual cells in complex multicellular organisms by understanding their physical location in tissue sections. In particular, in related research on tumour heterogeneity, ST is an excellent complementary approach to scRNA-seq, constituting a new method for further exploration of tumour heterogeneity, and this approach can also provide unprecedented insight into the development of treatments for pancreatic cancer (PC). In this review, based on the methods of scRNA-seq and ST analyses, research progress on the tumour microenvironment and treatment of pancreatic cancer is further explained.

Natural history and growth prediction model of pancreatic serous cystic neoplasms

OBJECTIVE

Serous cystic neoplasms (SCN) are benign pancreatic cystic neoplasms that may require resection based on local complications and rate of growth. We aimed to develop a predictive model for the growth curve of SCNs to aid in the clinical decision making of determining need for surgical resection.

METHODS

Utilizing a prospectively maintained pancreatic cyst database from a single institution, patients with SCNs were identified. Diagnosis confirmation included imaging, cyst aspiration, pathology, or expert opinion. Cyst size diameter was measured by radiology or surgery. Patients with interval imaging ≥3 months from diagnosis were included. Flexible restricted cubic splines were utilized for modeling of non-linearities in time and previous measurements. Model fitting and analysis were performed using R (V3.50, Vienna, Austria) with the rms package.

RESULTS

Among 203 eligible patients from 1998 to 2021, the mean initial cyst size was 31 mm (range 5-160 mm), with a mean follow-up of 72 months (range 3-266 months). The model effectively captured the non-linear relationship between cyst size and time, with both time and previous cyst size (not initial cyst size) significantly predicting current cyst growth (p < 0.01). The root mean square error for overall prediction was 10.74. Validation through bootstrapping demonstrated consistent performance, particularly for shorter follow-up intervals.

CONCLUSION

SCNs typically have a similar growth rate regardless of initial size. An accurate predictive model can be used to identify rapidly growing outliers that may warrant surgical intervention, and this free model (https://riskcalc.org/SerousCystadenomaSize/) can be incorporated in the electronic medical record.

Pancreatectomy for intraductal papillary mucinous neoplasm: has anything changed in North America?

BACKGROUND

Multiple guidelines on the management of intraductal papillary mucinous neoplasm (IPMN) have been published over the past decade. However, practice data are lacking. This study aims to determine whether pancreatectomy procedures, IPMN pathology, or outcomes have changed.

METHODS

ACS-NSQIP Procedure Targeted Pancreatectomy database was queried for patients with IPMN from 2014 to 2019. Cases were stratified by pathology, tumor stage/cyst size and procedure. Pancreatectomies for IPMN by year, 30-day morbidity, and clinically relevant postoperative pancreatic fistula (CR-POPF) were quantified. Mann-Kendall trend tests were performed to assess surgical trends and associated outcomes over time.

RESULTS

3912 patients underwent pancreatectomy for IPMN. 21% demonstrated malignancy and 79% were benign. Morbidity and mortality occurred in 29.7% and 1.5% of cases, respectively. Over time, no change was observed in use of pancreatectomy for IPMN (10%) or in benign/malignant pathology, or cyst size. Robotic approach increased from 9.1% to 16.5% with decreases in laparoscopic (19.5%-15.0%) and open interventions (71.5%-68.1%, p = 0.016). No change was observed over time in morbidity or mortality; however, rates of CR-POPF decreased (18.8%-13.8%, p < 0.001).

CONCLUSIONS

Practice patterns in treatment of IPMN have not changed significantly in North America. More patients are undergoing robotic pancreatectomy, and postoperative pancreatic fistula rates are improving.

Rare Non-Neuroendocrine Pancreatic Tumours

The most common tumour of the pancreas is ductal adenocarcinoma (PDAC). It remains one of the most lethal non-neuroendocrine solid tumours despite the use of a multi-approach strategy. Other, less-common neoplasms, which are responsible for 15% of pancreatic lesions, differ in treatment and prognosis. Due to the low incidence rate, there is a lack of information about the rarest pancreatic tumours. In this review, we described six rare pancreatic tumours: intraductal papillary mucinous neoplasm (IPMN), mucinous cystadenoma (MCN), serous cystic neoplasm (SCN), acinar cell carcinoma (ACC), solid pseudopapillary neoplasm (SPN) and pancreatoblastoma (PB). We distinguished their epidemiology, clinical and gross features, covered the newest reports about courses of treatment and systematised differential diagnoses. Although the most common pancreatic tumour, PDAC, has the highest malignant potential, it is still essential to properly classify and differentiate less-common lesions. It is vital to continue the search for new biomarkers, genetic mutations and the development of more specific biochemical tests for determining malignancy in rare pancreatic neoplasms.

Multidimensional Immunophenotyping of Intraductal Papillary Mucinous Neoplasms Reveals Novel T Cell and Macrophage Signature

BACKGROUND

Intraductal papillary mucinous neoplasms (IPMN) are the only radiographically identifiable precursor to pancreatic adenocarcinoma, yet little is known about how these lesions progress to cancer. Inflammation has been associated with dysplastic progression; however, the cause and composition of this inflammation remains poorly characterized. We sought to comprehensively profile immune cell infiltration using parallel spatial transcriptomic and flow cytometric techniques.

METHODS

Twelve patients with resected IPMN exhibiting both high-grade dysplasia (HGD) and low-grade dysplasia (LGD) were selected for spatial transcriptomics (NanoString GeoMx). Immune (CD45⁺), epithelial (PanCK⁺), and stromal (SMA⁺) compartments were analyzed separately using the GeoMx NGS Pipeline. An additional 11 patients resected for IPMN of varying degrees of dysplasia underwent immunophenotyping using flow cytometry (DURAClone IM).

RESULTS

Spatial transcriptomics revealed that T cells represent the dominant immune cell within IPMN stroma, which was confirmed by flow cytometry (56%). Spatial profiling found that the T-cell infiltrate was significantly higher in regions of LGD compared with HGD (62% vs. 50%, p = 0.038). Macrophages were the only other immune cell type with > 10% abundance, yet conversely, were generally more abundant in regions of HGD compared to LGD (19% vs. 11%, p = 0.058). Correspondingly, immune cells within regions of HGD demonstrated transcriptional upregulation of genes associated with macrophage activity including secretion (CXCL1) and phagocytosis (C1QA, C1S, C4B).

CONCLUSIONS

IPMN immune infiltrate is primarily composed of T cells and macrophages. Regions of HGD appear to be relatively deplete of T cells and show a trend toward macrophage enrichment compared with regions of LGD.

Progression vs Cyst Stability of Branch-Duct Intraductal Papillary Mucinous Neoplasms After Observation and Surgery

Importance

The progression of intraductal papillary mucinous neoplasms (IPMNs) of the pancreas to malignant disease is still poorly understood. Observational and surgical series have failed to provide comprehensive information.

Objective

To identify dynamic variables associated with the development of malignant neoplasms by combining pathological features with data from preoperative repeated observations.

Design, Setting, and Participants

The Crossover Observational Multicentric Study included a retrospective cohort of patients with branch-duct IPMNs (BD IPMNs) enrolled in a surveillance program from January 1, 2000, to December 31, 2019. Patients were enrolled from 5 referral centers: the Pancreas Institute, Verona, Italy; Seoul National University Hospital, Seoul, South Korea; Singapore General Hospital, Singapore; Johns Hopkins School of Medicine, Baltimore, Maryland; and University of Texas MD Anderson Cancer Center, Houston. Patients underwent a minimum of 12 months of preoperative surveillance (median, 37 [interquartile range (IQR), 20-68] months).

Main Outcomes and Measures

Dynamic variables associated with malignant disease were explored to estimate the presence of high-grade dysplasia (HGD) and invasive cancer at final pathological examination.

Results

A total of 292 patients were included in the analysis (137 women [46.9%] and 155 men [53.1%]; median age, 64 [IQR, 56-71] years). During surveillance, 27 patients (9.2%) developed a worrisome feature after 5 years, and 46 of 276 (16.7%) developed high-risk stigmata (HRS). At final pathological evaluation, 107 patients (36.6%) had HGD or invasive cancer, and 16 (5.5%) had IPMNs with concomitant pancreatic ductal adenocarcinoma. Rates of HGD and invasive cancer at pathological evaluation significantly differed between those without worrisome features and those developing HRS from a previous worrisome feature (9 [27.3%] vs 13 [61.9%]; P < .001). Developing an additional worrisome feature during surveillance (odds ratio [OR], 3.24 [95% CI, 1.38-7.60]; P = .007) or an HRS from a baseline worrisome feature (OR, 2.87 [95% CI, 1.01-8.17]; P = .048) was associated with HGD at final pathological evaluation. Among HRS, development of jaundice on a low-risk cyst was independently associated with invasive cancer (OR, 16.04 [95% CI, 2.94-87.40]; P = .001).

Conclusions and Relevance

These findings suggest that in BD IPMNs under surveillance, harboring a stable worrisome feature carries the lowest risk of malignant disease. Development of additional worrisome features or HRS is associated with the presence of HGD, whereas the occurrence of jaundice is associated with invasive cancer.