Osteoclast-like giant cell tumors of the pancreas: Clinical characteristics, genetic testing, and treatment modalities.

Abstract

e16752 Background: Undifferentiated osteoclast-like giant cell carcinoma of the pancreas is an aggressive malignancy only described by a few case reports in the literature. In this study, we sought to better characterize this entity by examining patients seen at Mayo Clinic. Methods: This study identified patients with osteoclast-like giant cell carcinoma of the pancreas using Mayo Clinic databases (MN, AZ, FL) from the year 2000 to present. Patient demographics, genetic data, and treatment modalities were reviewed. Kaplan-Meier analysis was used to evaluate median overall survival (mOS) for the cohort as well as mOS and mPFS for treatment subgroups. Results: 15 patients were identified (9 female, 6 male). Median age at diagnosis was 59 years and mOS for all patients was 11.0 mos (95% CI 6.2-15.7 mos). 3 patients (20%) had metastatic disease at diagnosis with the liver being the most common site (n = 3). Metastatic disease was associated with significantly shorter OS (3.5 vs. 14.1 mos, p = 0.005; HR 7.98 [95% CI 1.43-44.4]) compared to locoregional disease (LRD). 4 patients underwent genetic testing. The most common mutation was CDKN2A (n = 3), followed by TP53 (n = 2) and KRAS (n = 2). 13/15 patients had detailed follow-up information. 6/7 patients undergoing chemotherapy received a gemcitabine-based regimen as first line: with capecitabine (n = 2), with nab-paclitaxel (n = 2), or as monotherapy (n = 2). 1 patient received FOLFIRINOX. In patients with LRD and adequate follow-up (n = 11), 8/11 underwent surgical resection and had longer OS compared to those without resection (17.0 vs. 8.4 mos, p = 0.09). No surgical patients received neoadjuvant chemotherapy. 5/8 received adjuvant chemotherapy, 2 did not undergo chemotherapy, and 1 was lost to follow-up after surgery. PFS from time of surgery was 15.3mos (95% CI 5.0-25.6mos). 6 patients (40%) were alive at time of analysis; all 6 underwent surgical resection. Conclusions: Osteoclast-like giant cell carcinoma of the pancreas is a rare malignancy with a poor prognosis, even when diagnosed at an early stage. OS for patients of all stages in this study was less than 1 year suggesting prognosis may be even worse than that of pancreatic adenocarcinoma. The optimal therapy remains unknown but most patients received similar chemotherapy as in adenocarcinoma. Patients with LRD amenable to surgical resection experienced a PFS over 1 year from surgery, possibly associated with OS benefit, however overall prognosis is poor. Further study is warranted on a larger scale to better understand disease course and treatment options.