Introduction
Pancreatic adenocarcinoma has a poor prognosis with an overall 5-year survival rate of 10% as most patients present with unresectable or metastatic disease. Evaluation of microsatellite instability (MSI) or deficient DNA mismatch repair (dMMR) status can tailor treatment to increase the efficacy of systematic therapy. However, the adequacy of tissue samples obtained by routine endoscopic ultrasound-guided fine needle biopsy (EUSFNB) of pancreatic adenocarcinoma for MSI/dMMR assessment remains unclear. This study evaluated the role of EUSFNB using the Procore (Cook Medical) biopsy needles for MSI/dMMR assessment. In recent years, a new 20G Procore needle has been developed to overcome the limitations of tissue acquisition of the smaller needles (22G,25G) and the rigidity of the larger one (19G). We also aimed to study the performance assessment between Procore 20G vs 22G needles in tissue acquisition for MSI/dMMR assessment.
Aims & Methods
This was a single-centre study reviewed patients with suspected pancreatic adenocarcinoma who underwent diagnostic EUSFNB in a tertiary referral centre using either 20G or 22G Procore needles from January 2022 to March 2023. The newer 20G Procore needle was designed with a forward side-bevel, whereas the 22G needle had a reverse side-bevel, for tissue core acquisition. Clinical data and characteristics of lesions in all patients undergoing EUSFNB in the participating site are prospectively maintained in a registry for quality control and audit purposes. All cases of adenocarcinoma were tested for MSI/dMMR status by immunochemistry (MLH1, MSH2, MSH6 & PMS2). The primary study outcome measure was the adequacy of tissue samples for MSI/dMMR testing. Secondary outcomes were the rate of histological core tissue acquisition, the difference in the adequacy of tissue for MSI/dMMR testing between 20G and 22G Procore needles and the rate of MSI-high pancreatic adenocarcinoma. The impact of the use of these needles in obtaining adequate tissue on patient management was also evaluated.
Results
A total of 31 patients (mean age 68.2 SD± 8.17; 51% male) with pancreatic adenocarcinoma were included in the study. The mean size for the pancreatic mass was 33.17 SD±20.4 with most of the pancreatic mass located at the pancreatic head, uncinate, and neck region 70% (21/31). The histological yield of EUSFNB was 100%. Overall tissue adequacy rate for MSI/dMMR assessment was 80% (25/31), which was higher with 20G compared to 22G Procore needles (88.8%;16/18 vs 69.2%;9/13, p-value = 0.207). Two of the 23 patients with successful MSI/dMMR testing (8.7%) had MSI-high status. One received second-line treatment with pembrolizumab, and the other received the best supportive care due to worsening liver function and poor functional status.
Conclusion
This study affirmed the feasibility of routine MSI testing from specimens acquired by EUSFNB using the Procore EUSFNB needles. Our results also suggested that the larger 20G Procore needle with forward side-bevel had a higher yield for MSI testing than the 22G needle with reverse side-bevel, even though both needle types could obtain tissue cores for histology, and this should be reassessed by a further study with larger sample size that is adequately powered.
Disclosure
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