Immunohistochemical FAP Expression Reflects 68Ga-FAPI PET Imaging Properties of Low- and High-Grade Intraductal Papillary Mucinous Neoplasms and Pancreatic Ductal Adenocarcinoma

Pancreatic intraductal papillary mucinous neoplasms (IPMNs) are grossly visible (typically > 5 mm) intraductal epithelial neoplasms of mucin-producing cells, arising in the main pancreatic duct or its branches. According to the current 2-tiered grading scheme, these lesions are categorized as having either low-grade (LG) dysplasia, which has a benign prognosis, or high-grade (HG) dysplasia, which formally represents a carcinoma in situ and thus can transform to pancreatic ductal adenocarcinoma (PDAC). Because both entities require different treatments according to their risk of becoming malignant, a precise pretherapeutic diagnostic differentiation is inevitable for adequate patient management. Recently, our group has demonstrated that 68Ga-fibroblast activation protein (FAP) inhibitor (FAPI) PET/CT shows great potential for the differentiation of LG IPMNs, HG IPMNs, and PDAC according to marked differences in signal intensity and tracer dynamics. The purpose of this study was to biologically validate FAP as a target for PET imaging by analyzing immunohistochemical FAP expression in LG IPMNs, HG IPMNs, and PDAC and comparing with SUV and time to peak (TTP) measured in our prior study. Methods: To evaluate the correlation of the expression level of FAP and α-smooth muscle actin (αSMA) in neoplasm-associated stroma depending on the degree of dysplasia in IPMNs, 98 patients with a diagnosis of LG IPMN, HG IPMN, PDAC with associated HG IPMN, or PDAC who underwent pancreatic surgery at the University Hospital Heidelberg between 2017 and 2023 were identified using the database of the Institute of Pathology, University Hospital Heidelberg. In a reevaluation of hematoxylin- and eosin-stained tissue sections of formalin-fixed and paraffin-embedded resection material from the archive, which was originally generated for histopathologic routine diagnostics, a regrading of IPMNs was performed by a pathologist according to the current 2-tiered grading scheme, consequently eliminating the former diagnosis of "IPMN with intermediate-grade dysplasia." For each case, semithin tissue sections of 3 paraffin blocks containing neoplasm were immunohistologically stained with antibodies directed against FAP and αSMA. In a masked approach, a semiquantitative analysis of the immunohistochemically stained slides was finally performed by a pathologist by adapting the immunoreactive score (IRS) and human epidermal growth factor receptor 2 (Her2)/neu score to determine the intensity and percentage of FAP- and αSMA-positive cells. Afterward, the IRS of 14 patients who underwent 68Ga-FAPI-74 PET/CT in our previous study was compared with their SUVmax, SUVmean, and TTP for result validation. Results: From 98 patients, 294 specimens (3 replicates per patient) were immunohistochemically stained for FAP and αSMA. Twenty-three patients had LG IPMNs, 11 had HG IPMNs, 10 had HG IPMNs plus PDAC, and 54 had PDAC. The tumor stroma was in all cases variably positive for FAP. The staining intensity, percentage of FAP-positive stroma, IRS, and Her2/neu score increased with higher malignancy. αSMA expression could be shown in normal pancreatic stroma as well as within peri- and intraneoplastic desmoplastic reaction. No homogeneous increase in intensity, percentage, IRS, and Her2/neu score with higher malignancy was observed for αSMA. The comparison of the mean IRS of FAP with the mean SUVmax, SUVmean, and TTP of 68Ga-GAPI-74 PET/CT showed a matching value increasing with higher malignancy in 68Ga-FAPI-74 PET imaging and immunohistochemical FAP expression. Conclusion: The immunohistochemical staining of IPMNs and PDAC validates FAP as a biology-based stromal target for in vivo imaging. Increasing expression of FAP in lesions with a higher degree of malignancy matches the expectation of a stronger FAP expression in PDAC and HG IPMNs than in LG IPMNs and corroborates our previous findings of higher SUVs and a longer TTP in PDAC and HG IPMNs than in LG IPMNs.

Comparison of early and late 68Ga-FAPI-46-PET in 33 patients with possible recurrence of pancreatic ductal adenocarcinomas

Positron emission tomography with 68Gallium (68Ga) labeled inhibitors of fibroblast activation protein (68Ga-FAPI-PET) is a promising imaging technique for patients with recurrent pancreatic ductal adenocarcinomas (PDAC). To date, it is not clear if different acquisition timepoints for 68Ga-FAPI-PET may result in comparable imaging information and if repetitive 68Ga-FAPI-PET imaging may add diagnostic value to single timepoint acquisition for recurrent PDAC. Here we analyzed retrospectively early (20 min p.i.) and late (60 min p.i.) 68Ga-FAPI-PET imaging using FAPI-46 of 33 patients with possible recurrence of PDAC concerning detection rates and uptake over time of local recurrences, metastases, inflammatory lesions of the pancreas, cholestatic lesions of the liver and reactive tissue. 33 patients with histologically confirmed PDAC after complete or partial resection of the pancreas and possible recurrence were examined by 68Ga-FAPI-46-PET acquired 20- and 60-min post injection (p.i.) of the radiotracer. FAPI-positive lesions were classified as local recurrences, metastases, inflammatory lesions of the pancreas (ILP), cholestatic lesions of the liver and reactive tissue based on histology, PET- and CT-morphology and clinical information. Lesions were contoured, and standardized uptake values (SUVmax and SUVmean) and target-to-background ratios (TBR) were analyzed for both acquisition timepoints. In total, 152 FAPI-positive lesions (22 local relapses, 47 metastases, 26 inflammatory lesions of the pancreas, 28 reactive tissues, and 29 cholestatic lesions) were detected. Detection rates for the early and late acquisition of 68Ga-FAPI-46-PET were almost identical except cholestatic lesions, which showed a higher detection rate at early imaging. SUV parameters and TBRs of ILP significantly decreased over time. Cholestatic lesions showed a tendency towards decreasing uptake. All other types of lesions showed relatively stable uptake over time. Early and late acquisition of 68Ga-FAPI-PET results in comparable imaging information in patients with possible recurrence of PDAC. Two timepoint imaging offers additional diagnostic potential concerning differential diagnoses.

Static and Dynamic 68Ga-FAPI PET/CT for the Detection of Malignant Transformation of Intraductal Papillary Mucinous Neoplasia of the Pancreas

Pancreatic ductal adenocarcinoma (PDAC) may arise from intraductal papillary mucinous neoplasms (IPMN) with malignant transformation, but a significant portion of IPMN remains to show benign behavior. Therefore, it is important to differentiate between benign IPMN and IPMN lesions undergoing malignant transformation. However, nonoperative differentiation by ultrasound, CT, MRI, and carbohydrate antigen 19-9 (CA19-9) is still unsatisfactory. Here, we assessed the clinical feasibility of additional assessment of malignancy by PET using ⁶⁸Ga-labeled fibroblast activation protein inhibitors (⁶⁸Ga-FAPI PET) in 25 patients with MRI- or CT-proven cystic pancreatic lesions. Methods: Twenty-five patients with cystic pancreatic lesions who were followed up in the European Pancreas Center of Heidelberg University hospital and who were led to surgical resection or fine-needle aspiration due to suspicious clinical, laboratory chemistry, or radiologic findings were examined by static (all patients) and dynamic (20 patients) ⁶⁸Ga-FAPI PET. Cystic pancreatic lesions were delineated and SUV_max and SUV_mean were determined. Time-activity curves and dynamic parameters (time to peak, K ₁, k ₂, K3, k ₄) were extracted from dynamic PET data. Receiver-operating curves of static and dynamic PET parameters were calculated. Results: Eleven of the patients had menacing IPMN (high-grade IPMN with [6 cases] or without [5 cases] progression into PDAC) and 11 low-grade IPMN; 3 patients had other benign entities. Menacing IMPN showed significantly elevated ⁶⁸Ga-FAPI uptake compared with low-grade IPMN and other benign cystic lesions. In dynamic imaging, menacing IPMN showed increasing time-activity curves followed by slow decrease afterward; time-activity curves of low-grade IPMN showed an immediate peak followed by rapid decrease for about 10 min and slower decrease for the rest of the time. Receiver-operating curves showed high sensitivity and specificity (area under the curve greater than 80%) of static and dynamic PET parameters for the differentiation of IPMN subtypes. Conclusion: ⁶⁸Ga-FAPI PET is a helpful new tool for the differentiation of menacing and low-grade IPMN and shows the potential to avoid unnecessary surgery for nonmalignant pancreatic IPMN.

Myofibroblastic CAF Density, Not Activated Stroma Index, Indicates Prognosis after Neoadjuvant Therapy of Pancreatic Carcinoma

Neoadjuvant therapy (NT) for advanced PDAC is an emerging concept, affecting both stroma and tumor. The Activated Stroma Index (ASI; ratio of activated cancer-associated fibroblasts (CAF) to collagen deposition) is a prognostic marker in upfront resected pancreatic adenocarcinoma (PDAC). We assessed ASI and its prognostic relevance after NT. Tissue from resection specimens of n = 48 PDAC patients after neoadjuvant chemotherapy with FOLFIRINOX (FOL; n = 31), gemcitabine + nab-paclitaxel (GEM; 7) or combination treatment (COMB; 10) was compared with upfront resected matched controls (RES; 69). Activated CAFs were assessed by immunohistochemistry for α-SMA, and collagen was stained with aniline blue; the stained area was then determined by computational imaging analysis and ASI was calculated. In GEM, ASI was significantly higher and collagen deposition lower than in controls and FOL. The lowest quartile of ASI values had significantly longer overall survival (OS) in RES, whereas in FOL, the highest quartile had the best prognosis. After NT, OS was significantly improved in the α-SMA-high group; in RES, however, survival was independent of α-SMA. Reversed prognostic association of ASI thus points to the differing significance of stromal composition after FOL, while improved prognosis with high CAF abundance suggests a synergistic effect of myofibroblasts with chemotherapy. These divergences impede usability of ASI after NT.

Open irreversible electroporation for isolated local recurrence of pancreatic ductal adenocarcinoma after primary surgery

BACKGROUND/OBJECTIVES

Irreversible electroporation (IRE) is an emerging treatment for locally advanced pancreatic cancer (LAPC) which in some cohorts has been associated with severe complications. Additionally, re-resection of isolated local recurrence (ILR) after pancreatic ductal adenocarcinoma (PDAC) can improve survival. We investigated safety, feasibility and oncologic outcomes in the first report on open IRE for unresectable ILR of PDAC in a staged surgical approach.

METHODS

Records of the prospectively documented institutional database were screened for patients undergoing laparotomy in IRE-standby due to questionable resectability. Endpoints were morbidity, mortality and overall (OS) and progression free survival (PFS). Data of LAPC and ILR were compared statistically for safety and feasibility analysis.

RESULTS

Intraoperative IRE was performed in 11 ILR and 14 LAPC. Six (54.5%) ILR and 10 (71.4%) LAPC patients had postoperative complications, type and frequency did not differ significantly. Major complications occurred in one ILR and two LAPC patients. Median OS was 20.0 months (95% CI: 2.7-37.3) after IRE for ILR and 28 (17.4-38.6) for LAPC. Median PFS after IRE was seven months for both ILR (4.1-9.9; n = 9) and LAPC (2.3-11.7; n = 13).

CONCLUSION

Open IRE for unresectable ILR was associated with acceptable perioperative risk. In this small, highly selected subset of patients with limited therapeutic options ancillary treatment with IRE might improve survival. Randomized treatment studies are required to establish the definitive role of IRE as compared to palliative standards of care in unresectable recurrence of PDAC and inconvertible LAPC.

Efficacy of Pasireotide for Prevention of Postoperative Pancreatic Fistula in Pancreatic Surgery: a Systematic Review and Meta-analysis

BACKGROUND

Pasireotide was recently suggested for the prevention of postoperative pancreatic fistula (POPF) after pancreatic surgery. However, its efficacy remains to be controversially dicussed. Therefore, we conducted a systematic review and meta-analysis to assess the efficacy of pasireotide for preventing POPF after pancreatic surgery.

METHOD

A systematic literature search was conducted in PubMed, Web of Science, and The Cochrane Library to identify clinical studies investigating the efficacy of pasireotide after pancreatic surgery. The identified studies were critically appraised, and meta-analyses were then performed. The study was performed in accordance with PRISMA guidelines and was registered at the PROSPERO study database (CRD42018112334).

RESULTS

Four studies with a total of 919 patients were included: 418 with pasireotide treatment and 501 controls. Meta-analysis showed that pasireotide could reduce neither clinically relevant POPF rate (OR = 0.78; 95% CI, 0.49-1.24; P = 0.29) nor overall POPF rate (OR = 0.94; 95% CI, 0.60-1.48; P = 0.80) after pancreatic resections. There were no significant differences in delayed gastric emptying, mortality, and postoperative hospital stay after pancreatic surgery. However, pasireotide reduces readmission after pancreatic surgery (OR = 0.61; 95% CI, 0.44-0.85; P = 0.004). Subgroup analyses revealed that prophylactic use of pasireotide did not reduce the incidence of clinically relevant POPF after pancreaticoduodenectomy or distal pancreatectomy compared with the control.

CONCLUSION

Based on the available evidence, use of pasireotide may not reduce clinically relevant POPF as well as it may not improve postoperative course substantially after pancreatic surgery. Further investigator-initiated high-quality trials are needed.

Predictive performance of factors associated with malignancy in intraductal papillary mucinous neoplasia of the pancreas

Background

Estimation of the risk of malignancy in intraductal papillary mucinous neoplasia (IPMN) of the pancreas is a clinical challenge. Several routinely used clinical factors form the basis of the current consensus guidelines. This study aimed to determine the predictive values of the most commonly assessed risk factors.

Methods

A meta-analysis of individual risk factors of malignancy in IPMN was performed. Contingency tables were derived from these data, and sensitivity, specificity, negative and positive predictive values, and diagnostic odds ratios (DOR) were determined. Hierarchical summary receiver operating characteristic (HSROC) curves for each factor were calculated and the respective area under the curve (AUC) was assessed.

Results

A total of 3443 studies were screened initially. Analysis of recent literature revealed 60 studies with 13 relevant risk factors including clinical, serological and radiological parameters. The largest area under the HSROC curve was found for weight loss (0·84) and jaundice/raised bilirubin level (0·80), followed by increased carcinoembryonic antigen (CEA) (0·79) or carbohydrate antigen (CA) 19-9 (0·78) levels. The most sensitive factors were patient age (71 per cent) and mural nodules (65 per cent), and jaundice/raised bilirubin level (97 per cent) and increased CEA level (95 per cent) were most specific. None of the analysed factors reached a positive or negative level of prediction beyond 90 per cent.

Conclusion

None of the established criteria safely distinguishes malignant from non-malignant lesions.

Incidence, risk factors and clinical implications of chyle leak after pancreatic surgery

Background

Chyle leak is a well known but poorly characterized complication after pancreatic surgery. Available data on incidence, risk factors and clinical significance of chyle leak are highly heterogeneous.

Methods

For this cohort study all patients who underwent pancreatic surgery between January 2008 and December 2012 were identified from a prospective database. Chyle leak was defined as any drainage output with triglyceride content of 110 mg/dl or more. Risk factors for chyle leak were assessed by univariable and multivariable analyses. The clinical relevance of chyle leak was evaluated using hospital stay and resolution by 14 days for short-term outcome and overall survival for long-term outcome.

Results

Chyle leak developed in 346 (10·4 per cent) of 3324 patients. Pre-existing diabetes, resection for malignancy, distal pancreatectomy, duration of surgery 180 min or longer, and concomitant pancreatic fistula or abscess were independent risk factors for chyle leak. Both isolated chyle leak and coincidental chyle leak (with other intra-abdominal complications) were associated with prolonged hospital stay. Some 178 (87·7 per cent) of 203 isolated chyle leaks and 90 (70·3 per cent) of 128 coincidental chyle leaks resolved with conservative management within 14 days. Initial and maximum drainage volumes were associated with duration of hospital stay and success of therapy by 14 days. Impact on survival was restricted to chyle leaks that persisted at 14 days in patients with cancer undergoing palliative surgery.

Conclusion

Chyle leak is a relevant complication, with an incidence of more than 10 per cent after pancreatic surgery, and has a major impact on hospital stay. Drainage volume is associated with hospital stay and success of therapy.

Postoperative pancreatic fistula: We need to redefine grades B and C

BACKGROUND

Postoperative pancreatic fistula (POPF) is the most important complication after pancreatic surgery. In 2005, the International Study Group of Pancreatic Surgery (ISGPS) introduced a standardized POPF definition with severity grading from A to C. In recent years, interventional drainage (ID) has become the standard of care for symptomatic postoperative fluid collections or undrained POPF. From the original definition, it is unclear whether ID is categorized as POPF grade B or C. Therefore, international authors shift ID between grades B and C. The aim of the study was to analyze patients with ID (proposed new grade B) versus patients who underwent reoperation (grade C) for POPF.

METHODS

Between 2005 and 2013, all patients undergoing pancreatic resection were analyzed regarding POPF grade A-C. Demographic data, type of operation, postoperative complications, therapies and outcome were examined with focus on ID versus reoperation.

RESULTS

Of the 2,955 patients included, 403 developed POPF (13.6%). Among all POPF, 11% were grade A, 17% grade B (clinically symptomatic without ID), and 72% grade C. These patients underwent either ID (n = 165) or reoperation (n = 123). Patients with ID had an average hospital stay of 33 days and POPF-associated mortality of 0%. This was strikingly different from patients undergoing reoperation with a hospital stay of 47 days and POPF-associated mortality of 37% (P < .0001).

CONCLUSION

After 10 years of the ISGPS classification, there is a clear-cut outcome difference between patients undergoing POPF-associated ID or reoperation. We propose assigning all patients undergoing ID as POPF grade B. Patients undergoing reoperation should definitely remain within category C.

Neutrophil granulocyte derived MMP-9 is a VEGF independent functional component of the angiogenic switch in pancreatic ductal adenocarcinoma

BACKGROUND

Vascular endothelial growth factor (VEGF) that is secreted by tumor cells plays a key role in angiogenesis. Matrix metalloproteinase 9 (MMP-9) is produced by inflammatory cells, such as stromal granulocytes (PMN), remodels the extracellular matrix and is known to promote angiogenesis indirectly by interacting with VEGF. The aim of this study was to determine the role of PMN-derived MMP-9, its interaction with VEGF, and the efficacy of anti-angiogenic therapy targeting MMP-9 with oral Doxycycline and VEGF with Bevacizumab in pancreatic cancer (PDAC).

METHODOLOGY/PRINCIPAL FINDINGS

Inhibitors to MMP-9 (Doxycycline) and VEGF (Bevacizumab) were used alone or in combination in an in vitro angiogenesis assay to test their effect on angiogenesis caused by MMP-9, VEGF, PMN and PDAC cells. In an in vivo model of xenografted PDAC, treatment effects after 14 days under monotherapy with oral Doxycycline or Bevacizumab and a combination of both were evaluated. In vitro, PMN-derived MMP-9 had a direct and strong proangiogenic effect that was independent and additive to PDAC-derived VEGF. Complete inhibition of angiogenesis required the inhibition of VEGF and MMP-9. In vivo, co-localization of MMP-9, PMN and vasculature was observed. MMP inhibition with oral Doxycycline alone resulted in a significant decrease in PDAC growth and mean vascular density comparable to VEGF inhibition alone.

CONCLUSIONS/SIGNIFICANCE

PMN derived MMP-9 acts as a potent, direct and VEGF independent angiogenic factor in the context of PDAC. MMP-9 inhibition is as effective as VEGF inhibition. Targeting MMP-9 in addition to VEGF is therefore likely to be important for successful anti-angiogenic treatment in pancreatic cancer.

[Costal osteoid osteoma]

We report about a rare case of osteoid osteoma of the 9th rib in a 32 year old woman. A search of medical literature yielded only 16 reports about costal osteoid osteoma. This tumor should be considered in cases of painful rib without anamnestic trauma.