Citations

Cancer stem cells (CSCs) are thought to be a distinct population of cells within a tumor mass that are capable of asymmetric division and known to have chemoresistant characteristics. The description and identification of CSC models in cancer growth and recurrence has inspired the design of novel treatment strategies to overcome treatment resistance by targeting both CSCs and non-CSC tumor cells. Several cellular signaling pathways have been described as playing a role in the induction and maintenance of stemness in CSCs, such as the Wnt/β-catenin, Notch, STAT3, and Hedgehog pathways. In this review, we aim to review some of the ongoing CSC therapeutic targeting strategies in gastrointestinal malignancies.

Abstract Cancer transmission with organ donation has been previously reported with a variety of malignancies and organ transplants. The risk of transmission through organ transplantation from donors with a history of previously treated malignancies has been addressed by guidelines from transplant societies. Herein, we report a case of a patient who developed lung cancer confined to the liver after liver transplantation with no known history of malignancy in the donor. The suspicion of donor origin arose after positron emission tomography-computerized tomography scan showed metastatic lung cancer only involving the transplanted liver without a primary focus. Genetic analysis of the malignant cells confirmed donor origin of the cancer.

619 Background: Regorafenib (at a starting dose of 160 mg/day, rego 160), regorafenib (with a weekly dose escalation, rego 80+) and TAS-102, are suggested treatment options for refractory metastatic colorectal cancer (mCRC). We aimed to evaluate the comparative effectiveness evidence supporting these 3 strategies. Methods: We searched PubMed, Embase, and Cochrane CENTRAL, for randomized controlled trials evaluating TAS 102 or regorafenib in refractory mCRC patients who progressed on/intolerant of previous oxaliplatin, irinotecan, and fluoropyrimidine. Outcomes of interest included OS and PFS. The overall effect was pooled using the DerSimonian random effects model. We conducted network meta-analysis based on White’s multivariate meta-regression to pool evidence from direct and indirect comparisons. Results: Six trials (3 of regorafenib and 3 of TAS-102) at low risk of bias (2,445 patients) were included. Direct comparisons showed that Rego 160 and TAS-102 as monotherapy were superior to BSC in terms of PFS (Rego 160: HR = 0.4, CI 0.26 to 0.63; TAS-102: HR = 0.46, CI 0.40 to 0.52) and OS (Rego 160: HR = 0.67, CI 0.48 to 0.93; TAS-102: HR = 0.67, CI 0.57 to 0.80). Network analysis showed that there was no difference in PFS or OS between Rego 160 and TAS-102. Rego 80+ was superior to BSC in terms of OS (HR = 0.44, CI 0.23 to 0.84) and PFS (HR = 0.37, CI 0.21 to 0.66). There was a numerical advantage for Rego 80+ compared to TAS-102 and Rego 160 (see table). Conclusions: Regorafenib 160 and TAS-102 appear to have similar efficacy. Rego 80+ is shown to be superior to BSC. A trend for improved OS was observed with Rego 80+ versus Rego 160 or TAS 102. [Table: see text]

355 Background: In this study, we sought to determine the prognostic factors impacting survival of patients with NELM who underwent LT at Mayo Clinic. Methods: We performed a three-site retrospective analysis of patients with unresectable NELM treated with LT from 1990 -2017. Cases were identified from clinical databases at Mayo Clinic. Data on demographics, timing of diagnosis and transplant, extent of liver involvement, and tumor grade, were extracted. Extent of liver involvement was calculated using previously validated standardized volumetry with high defined as > 25% increase in the weight of the extracted liver at the time of the transplant as compared to the standard liver volume. Survival was calculated using the Kaplan–Meier method. Results: We identified 37 patients. Median age at LT was 47 (range 17.0-64.0), male: female (73% vs. 27%, respectively). Primary tumor site was in the pancreas in 51.3% and in the small bowels in 43.2%; 78.4% had NELM at presentation. While primary tumor resection was done at the time of LT in 5 (13.9%) cases, most patients (80.6%) had ˃6-months interval between primary tumor resection and LT surgery. Prior to LT, 25 (74.3%) patients received somatostatin analogues and 18 (61.3%) had liver-directed therapy. Median time from diagnosis to transplant was 33.6 months (0-246). High extent of liver involvement was identified in 12 patients (33.3%). Disease-Free Survival (DFS) at 3, 5, and 10 years was 56.8%, 43.1%, and 22.4% respectively. Overall-survival (OS) at 3, 5, and 10 years was 86.9%, 79.6%, and 52.6% respectively. High extent of liver involvement at the time of transplantation was associated with inferior DFS and OS and patients˃45 years-old at the time of transplantation had worse DFS. Patients whose disease met the OPTN (Organ Procurement and Transplantation Network) criteria for NELM transplantation had significantly better DFS and OS with median 10-year OS of 80.7 % vs. 17%. Conclusions: LT is a reasonable therapeutic option for selected patients with unresectable NELM with 10-year OS of 52.6%. High extent of liver involvement was associated with worse long-term outcomes while meeting OPTN criteria resulted in best outcomes.

328 Background: Patients with a history of solid organ transplants have been excluded from PD-1/PD-L1 inhibitor clinical trials due to concern for graft rejection. Only 2 case reports of PD-1 inhibitor use in patients with liver transplantation (LT) have been reported thus far. Here, we report our experience with using checkpoint inhibitors in metastatic cancer patients with LT. Methods: A single center pilot evaluation was conducted to evaluate the safety and efficacy of PD-1/PD-L1 inhibitors in patients with LT. PD-L1 staining on both the tumor and allograft were assessed if there was available tissue. The primary endpoint was evaluation of the risk for allograft rejection. Secondary endpoints included RECIST v1.1 and Immune-Related Response criteria (iRC) response rates, progression free survival (PFS) and overall survival (OS). Translational objectives included the relationship of PD-L1/PD-1 staining of tumor/allograft with response and rejection. Results: Six metastatic cancer patients with a history of LT received PD-1 inhibitor therapy (hepatocellular n=5, melanoma n=1). 3 patients were on mTOR inhibitor as immunosuppressive regimen and 3 on calcineurin inhibitor. Overall, allograft rejection was observed in 1/6 patients (on mTOR inhibitor). One patient achieved a CR (melanoma), 3 patients had PD and 2 patients discontinued therapy prior to restaging assessments. A single response (by both RECIST v1.1 and iRC) and rejection were reported in patients who received mTOR inhibitors (1 of 3). Three patients were tested for PD-L1 staining in the allograft tissue and all of them were negative (0% staining) with no graft rejections observed. Four patients had tumor PD-L1 evaluated (2 patients tested positive with 1 patient obtained a CR). The median OS, PFS and duration of therapy were 1.2, 1.8 and 1.2 months respectively. Conclusions: In this pilot evaluation of PD-1/PD-L1 inhibitors in LT patients both preliminary efficacy (1 of 4) and allograft rejection (1 of 6) was exhibited. Larger, prospective trials are needed to elucidate optimal patient and immunosuppressive regimen selection in these patients.

e15779 Background: There is paucity of data regarding the best available second-line treatment following progression on gemcitabine-based regimens in metastatic pancreatic ductal adenocarcinoma (PDAC). While a Nanoliposomal formulation of irinotecan (MM398) is considered a standard of care, there is conflicting data relating to the use of oxaliplatin in this setting. We performed a meta-analysis to determine the effectiveness of adding oxaliplatin (OX) or various irinotecan (IRI) formulations to a fluoropyrimidine (FP) as a second-line in PDAC patients. Methods: We searched different databases, including PubMed, Embase and Cochrane, to identify randomized controlled trials comparing FP monotherapy to FP combination therapy that includes either oxaliplatin (FPOX) or various irinotecan formulations (FPIRI) in PDAC patients who progressed after first-line treatment. Secondary analyses were planned to assess the effectiveness of FPOX and FPIRI compared to FP. Outcomes of interest included overall survival (OS) and progression-free survival (PFS). The overall effect was pooled using the DerSimonian and Laird random effects models. Results: Five studies (2 with FPIRI and 3 with FPOX) with 895 patients were identified. Patients randomized to FPIRI/FPOX had a significantly improved PFS (HR = 0.74, CI 0.62 to 0.89) and a trend towards an improved OS compared to FP monotherapy (HR = 0.88, CI 0.65 to 1.19). When comparing FPIRI to FP, there was an improvement in both PFS (HR = 0.64, CI 0.47 to 0.87) and OS (HR = 0.70, CI 0.55 to 0.89) in patients treated with the combination. Conversely, FPOX showed only a modest improvement in PFS (HR = 0.81, CI 0.67, 0.97) with no improvement in OS (HR = 1.03, CI 0.64 to 1.67). Conclusions: Combination chemotherapy with oxaliplatin or various irinotecan formulations seem to improve PFS vs. single agent FP. FPIRI, but not FPOX seem to confer an OS advantage. Oxaliplatin with FP following gemcitabine failure may need further confirmatory studies to establish its role in refractory pancreas cancer.