Adjuvant therapy following resection for pancreatic adenocarcinoma

Construction of orthotopic xenograft mouse models for human pancreatic cancer

Animal models are indispensable for the study of tumorigenesis and the development of anti-cancer drugs for human pancreatic cancer. In the present study, two orthotopic xenograft mouse models were developed. AsPC-1 human pancreatic cancer cells were stably labeled with red fluorescent protein (RFP) and injected subcutaneously into nude mice. For the orthotopic tumor mass model, the formed subcutaneous tumors were cut into blocks and implanted into the pancreas of nude mice via laparotomy. For the Matrigel™ tumor block model, solidified Matrigel containing RFP-labeled AsPC-1 cells was cut into blocks and implanted into the pancreas of nude mice. A subcutaneous tumor xenograft model was used as a control. Tumor growth and metastasis were assessed using an in vivo fluorescence imaging system. Thirty-six days after implantation, all mice from the two orthotopic xenograft models (n=20 per group) and 55% of the subcutaneous xenograft mice (n=20) developed tumors. The tumor growth rate was significantly higher in the orthotopic models than that in the subcutaneous model (P<0.01). Metastasis to organs such as the liver was observed in the orthotopic tumor models. Histological examination showed that the tumors were poorly differentiated adenocarcinomas. In conclusion, two orthotopic xenograft mouse models of human pancreatic cancer were established; these exhibited greater tumor growth and metastasis than the subcutaneous xenograft mouse model.

Underuse of surgical resection among elderly patients with early-stage pancreatic cancer

BACKGROUND

Although surgery improves the health care quality and outcomes of patients with early-stage pancreatic cancer, these patients' operative resection rate has been historically low. We sought to identify factors that are associated with operative resection in this patient population.

METHODS

In this retrospective population-based study, we used Texas Cancer Registry-linked and Surveillance and Epidemiology End Results Program-linked Medicare data to study factors potentially associated with operative resection in patients age ≥ 66 years who had been diagnosed with localized pancreatic cancer between January 1, 2001, and December 31, 2009. Variables were assessed using multivariate logistic regression and Cox proportional hazards regression models. We used Kaplan-Meier analysis to assess the effect of operative resection on survival rate.

RESULTS

Of 1,501 patients with localized pancreatic cancer, only 340 (22.7%) underwent operation. Patients were more likely to undergo surgery if they were young, had small tumors, had low-grade tumors, and had nodal negativity (P < .05). Compared with patients who did not undergo surgery, patients who underwent surgery had a significantly higher 5-year overall survival rate (25.0 vs 2.3%; P < .0001) and had a higher median survival time (24.3 vs 5.8 months).

CONCLUSION

The rate of operative resection of early-stage pancreatic cancer did not increase significantly from 2001 to 2009. Although we identified several variables associated with operative resection, why the percentage of patients with localized pancreatic cancer who undergo definitive surgery is so low remains unclear.

Survival after pancreatectomy for pancreatic adenocarcinoma is not impacted by performance status

BACKGROUND

Patients with the best performance status have the best prognosis after resection for pancreatic adenocarcinoma. This study was undertaken to determine the impact of performance status on survival after pancreatectomy for adenocarcinoma.

METHODS

Patients with a Karnofsky Performance Score (KPS) status (KPS) ≥60 after pancreatectomy for adenocarcinoma were evaluated, and the impact of the KPS at 6 weeks after pancreatectomy on survival was determined using survival curve analysis.

RESULTS

Recurrence was experienced by 84% of patients and negatively impacted patient survival. The median overall survival was 12 months, and the 2-year overall survival was 35%. The KPS after pancreatectomy did not impact survival when using survival curve analysis (P = .5740).

CONCLUSIONS

Performance status for patients with a KPS ≥60 after pancreatectomy does not impact survival. Patients with pancreatic adenocarcinoma without adjuvant therapy have poor overall survival, and KPS after pancreatectomy for adenocarcinoma should not be used to withhold therapy for these patients.

The efficacy of a novel, dual PI3K/mTOR inhibitor NVP-BEZ235 to enhance chemotherapy and antiangiogenic response in pancreatic cancer

Gemcitabine has limited clinical benefits for pancreatic ductal adenocarcinoma (PDAC). The phosphatidylinositol-3-kinase (PI3K)/AKT and mammalian target of rapamycin (mTOR) signaling pathways are frequently dysregulated in PDAC. We investigated the effects of NVP-BEZ235, a novel dual PI3K/mTOR inhibitor, in combination with gemcitabine and endothelial monocyte activating polypeptide II (EMAP) in experimental PDAC. Cell proliferation and protein expression were analyzed by WST-1 assay and Western blotting. Animal survival experiments were performed in murine xenografts. BEZ235 caused a decrease in phospho-AKT and phospho-mTOR expression in PDAC (AsPC-1), endothelial (HUVECs), and fibroblast (WI-38) cells. BEZ235 inhibited in vitro proliferation of all four PDAC cell lines tested. Additive effects on proliferation inhibition were observed in the BEZ235-gemcitabine combination in PDAC cells and in combination of BEZ235 or EMAP with gemcitabine in HUVECs and WI-38 cells. BEZ235, alone or in combination with gemcitabine and EMAP, induced apoptosis in AsPC-1, HUVECs, and WI-38 cells as observed by increased expression of cleaved poly (ADP-ribose) polymerase-1 (PARP-1) and caspase-3 proteins. Compared to controls (median survival: 16 days), animal survival increased after BEZ235 and EMAP therapy alone (both 21 days) and gemcitabine monotherapy (28 days). Further increases in survival occurred in combination therapy groups BEZ235 + gemcitabine (30 days, P = 0.007), BEZ235 + EMAP (27 days, P = 0.02), gemcitabine + EMAP (31 days, P = 0.001), and BEZ235 + gemcitabine + EMAP (33 days, P = 0.004). BEZ235 has experimental PDAC antitumor activity in vitro and in vivo that is further enhanced by combination of gemcitabine and EMAP. These findings demonstrate advantages of combination therapy strategies targeting multiple pathways in pancreatic cancer treatment.

Evaluation of poly-mechanistic antiangiogenic combinations to enhance cytotoxic therapy response in pancreatic cancer

Gemcitabine (Gem) has limited clinical benefits in pancreatic ductal adenocarcinoma (PDAC). The present study investigated combinations of gemcitabine with antiangiogenic agents of various mechanisms for PDAC, including bevacizumab (Bev), sunitinib (Su) and EMAP II. Cell proliferation and protein expression were analyzed by WST-1 assay and Western blotting. In vivo experiments were performed via murine xenografts. Inhibition of in vitro proliferation of AsPC-1 PDAC cells by gemcitabine (10 µM), bevacizumab (1 mg/ml), sunitinib (10 µM) and EMAP (10 µM) was 35, 22, 81 and 6 percent; combination of gemcitabine with bevacizumab, sunitinib or EMAP had no additive effects. In endothelial HUVECs, gemcitabine, bevacizumab, sunitinib and EMAP caused 70, 41, 86 and 67 percent inhibition, while combination of gemcitabine with bevacizumab, sunitinib or EMAP had additive effects. In WI-38 fibroblasts, gemcitabine, bevacizumab, sunitinib and EMAP caused 79, 58, 80 and 29 percent inhibition, with additive effects in combination as well. Net in vivo tumor growth inhibition in gemcitabine, bevacizumab, sunitinib and EMAP monotherapy was 43, 38, 94 and 46 percent; dual combinations of Gem+Bev, Gem+Su and Gem+EMAP led to 69, 99 and 64 percent inhibition. Combinations of more than one antiangiogenic agent with gemcitabine were generally more effective but not superior to Gem+Su. Intratumoral proliferation, apoptosis and microvessel density findings correlated with tumor growth inhibition data. Median animal survival was increased by gemcitabine (26 days) but not by bevacizumab, sunitinib or EMAP monotherapy compared to controls (19 days). Gemcitabine combinations with bevacizumab, sunitinib or EMAP improved survival to similar extent (36 or 37 days). Combinations of gemcitabine with Bev+EMAP (43 days) or with Bev+Su+EMAP (46 days) led to the maximum survival benefit observed. Combination of antiangiogenic agents improves gemcitabine response, with sunitinib inducing the strongest effect. These findings demonstrate advantages of combining multi-targeting agents with standard gemcitabine therapy for PDAC.

RNAi knockdown of Hop (Hsp70/Hsp90 organising protein) decreases invasion via MMP-2 down regulation

We previously identified Hop as over expressed in invasive pancreatic cancer cell lines and malignant tissues of pancreatic cancer patients, suggesting an important role for Hop in the biology of invasive pancreatic cancer. Hop is a co-chaperone protein that binds to both Hsp70/Hsp90. We hypothesised that by targeting Hop, signalling pathways modulating invasion and client protein stabilisation involving Hsp90-dependent complexes may be altered. In this study, we show that Hop knockdown by small interfering (si)RNA reduces the invasion of pancreatic cancer cells, resulting in decreased expression of the downstream target gene, matrix metalloproteinases-2 (MMP-2). Hop in conditioned media co-immunoprecipitates with MMP-2, implicating a possible extracellular function for Hop. Knockdown of Hop expression also reduced expression levels of Hsp90 client proteins, HER2, Bcr-Abl, c-MET and v-Src. Furthermore, Hop is strongly expressed in high grade PanINs compared to lower PanIN grades, displaying differential localisation in invasive ductal pancreatic cancer, indicating that the localisation of Hop is an important factor in pancreatic tumours. Our data suggests that the attenuation of Hop expression inactivates key signal transduction proteins which may decrease the invasiveness of pancreatic cancer cells possibly through the modulation of Hsp90 activity. Therefore, targeting Hop in pancreatic cancer may constitute a viable strategy for targeted cancer therapy.

MR imaging for predicting the recurrence of pancreatic carcinoma after surgical resection

OBJECTIVE

To study the relationship of characteristics of pancreatic carcinoma on MR imaging to tumor recurrence time after surgical resection.

MATERIALS AND METHODS

Twenty-seven patients with pancreatic carcinoma were followed up at least 2 years after surgical resection of the tumor. All patients had MR imaging within 1 month before surgery. The tumor's size, signal intensity, local and vascular invasion, abdominal lymphadenopathy on MR imaging and the positive surgical margin were noted. The results from MR imaging were compared with the duration after surgery until tumor recurrence and with the positive surgical margin.

RESULTS

59% of patients had various degree of extrapancreatic invasion. The tumor recurrence times were, respectively, 24+/-21 months and 26+/-29 months in patients with and without vascular invasion (P=0.79). The combination of vascular with local invasion showed a correlation to the time of tumor recurrence (r=-0.34; P<0.05). Patients with positive surgical margins had a higher local invasion score on MR imaging and a shorter recurrence time than those with negative surgical margins. The number and size of lymph nodes were not related with tumor recurrence time.

CONCLUSION

MR imaging was useful for predicting the recurrence of pancreatic carcinoma after surgical resection. Local invasion associated with and without vascular invasion on MR imaging was the indicator for the tumor recurrence.

Intra-operative radiotherapy (IORT) in pancreatic cancer: joint analysis of the ISIORT-Europe experience

PURPOSE

A joint analysis of data from five contributing centers within the ISIORT-Europe program was performed to investigate the main contributions of intra-operative radiotherapy (IORT) to the multidisciplinary treatment of pancreatic cancer.

MATERIALS AND METHODS

Patients with a histologic diagnosis of carcinoma of the pancreas, with an absence of distant metastases, undergoing surgery with radical intent and IORT were considered eligible for participation in this study.

RESULTS

From 1985 to 2006, a total of 270 patients were enrolled in the study from five European institutions. Surgery was performed in 91.5% of cases and complicated by adverse events in 59 cases. External radiotherapy (ERT) preceded surgery in 23.9% of cases. One-hundred and six patients received further ERT. After surgery + IORT, median follow-up was 96 months (range 3-180). Median local control was 15 months, 5-year local control was 23.3%. Median overall survival was 19 months, while 5-year survival was 17.7%. A significantly greater local control and survival were observed in patients undergoing preoperative radiotherapy (LC: median not reached; OS: median 30 months) compared to patients treated with postoperative ERT alone (LC: median 28 months; OS: median 22 months), and to patients submitted to IORT exclusively (LC: median 8 months; OS: median 13 months) (p < 0.0001).

CONCLUSION

From this joint analysis emerges the fact that preoperative radiotherapy increases the effects of IORT in terms of local control and overall survival. The 5-year local control of 23.3% confirms the beneficial "sterilizing" effect of IORT on the tumor bed.

Quality of pancreatic cancer care at Veterans Administration compared with non-Veterans Administration hospitals

BACKGROUND

National efforts are underway to monitor the quality of patient care at Veterans Administration (VA) hospitals. The objective of this study was to examine treatment utilization and outcomes for localized pancreatic cancer at VA compared with non-VA hospitals.

METHODS

Using the National Cancer Data Base, patients with pretreatment clinical stage I/II pancreatic adenocarcinoma were identified. Treatment utilization and outcomes were assessed at VA compared with academic and community hospitals.

RESULTS

Of 35,009 patients, 2% were seen at VA, 38% at academic, and 54% at community hospitals. VA hospitals were more likely to use surgery (odds ratio 2.20, 95% confidence interval 1.73-2.79) and to administer adjuvant chemotherapy (odds ratio 1.77, confidence interval 1.28-2.46) compared with community hospitals. Adjusted perioperative mortality and 3-year survival rates after surgery were similar at VA and academic hospitals.

CONCLUSIONS

For localized pancreatic cancer, patients treated at VA hospitals receive stage-specific treatments and have risk-adjusted perioperative and long-term survival rates that are comparable with those for patients treated at academic centers.

Multimodality therapy for pancreatic cancer in the U.S. : utilization, outcomes, and the effect of hospital volume

BACKGROUND

Despite decreased perioperative morbidity and mortality and clinical trials suggesting improved outcomes with adjuvant therapy, national practice patterns in the management of pancreatic cancer remain poorly defined. The purpose of the current study was to evaluate multimodality therapy utilization and outcomes relative to hospital type and volume.

METHODS

Using the National Cancer Data Base, stage-specific treatment patterns were analyzed for 301,033 patients with pancreatic adenocarcinoma. Logistic regression was used to evaluate treatment utilization. Cox proportional hazards modeling was utilized to evaluate the effect of multimodality therapy on survival.

RESULTS

Stage at presentation did not differ from 1985-1994 to 1995-2003; however, the percentage of patients receiving cancer-directed treatment increased from 45.1% to 51.8% (P < .001). Pancreatectomy for localized disease (AJCC 6th edition stages I and II) increased from 36.9% to 49.3% (P < .001). After resection, the use of adjuvant chemotherapy alone increased from 4.1% to 5.7% (P < .001), but the use of adjuvant radiation alone decreased from 7.0% to 4.6% (P < .001). Adjuvant chemoradiation use increased from 26.8% to 38.7% (P < .001). The use of surgery alone decreased from 62.1% (5213 of 8400 cases) to 49.9% (10,807 of 21,679 cases) (P < .001). Patients with localized pancreatic cancer were more likely to receive pancreatectomy and adjuvant chemoradiation at academic and high-volume centers (P < .001). Survival for localized disease was better after surgery with adjuvant therapy (hazards ratio [HR], 0.44; 95% confidence interval [95% CI], 0.42-0.47) and surgical resection alone (HR, 0.54; 95% CI, 0.52-0.57) compared with no treatment.

CONCLUSIONS

To the authors' knowledge, the current study is the largest study regarding pancreatic cancer performed to date, and the first to investigate national practice patterns for multimodality therapy utilization. Multimodality therapy utilization has increased over time and appears to have a beneficial impact on survival.

National failure to operate on early stage pancreatic cancer

BACKGROUND

Despite studies demonstrating improved outcomes, pessimism persists regarding the effectiveness of surgery for pancreatic cancer. Our objective was to evaluate utilization of surgery in early stage disease and identify factors predicting failure to undergo surgery.

METHODS

Using the National Cancer Data Base (1995-2004), 9559 patients were identified with potentially resectable tumors (pretreatment clinical Stage I: T1N0M0 and T2N0M0). Multivariate models were employed to identify factors predicting failure to undergo surgery and assess the impact of pancreatectomy on survival.

RESULTS

Of clinical Stage I patients 71.4% (6823/9559) did not undergo surgery; 6.4% (616/9559) were excluded due to comorbidities; 4.2% (403/9559) refused surgery; 9.1% (869/9559) were excluded due to age; and 38.2% (3,644/9559) with potentially resectable cancers were classified as "not offered surgery." Of the 28.6% (2736/9559) of patients who underwent surgery, 96.0% (2630/2736) underwent pancreatectomy, and 4.0% (458/2736) had unresectable tumors. Patients were less likely to undergo surgery if they were older than 65 years, were black, were on Medicare or Medicaid, had pancreatic head lesions, earned lower annual incomes, or had less education (P < 0.0001). Patients were less likely to receive surgery at low-volume and community centers. Patients underwent surgery more frequently at National Cancer Institute/National Comprehensive Cancer Network-designated cancer centers (P < 0.0001). Patients who were not offered surgery had significantly better survival than those with Stage III or IV disease but worse survival than patients who underwent pancreatectomy for Stage I disease (P < 0.0001).

CONCLUSIONS

This is the first study to characterize the striking underuse of pancreatectomy in the United States. Of early stage pancreatic cancer patients without any identifiable contraindications, 38.2% failed to undergo surgery.

Delayed recovery after pancreaticoduodenectomy: a major factor impairing the delivery of adjuvant therapy?

BACKGROUND

Delayed recovery after pancreaticoduodenectomy (PD) is believed to preclude adjuvant therapy for approximately 30% of patients who undergo elective PD as initial treatment for pancreatic adenocarcinoma. This study reexamined the frequency of delayed recovery and assessed other factors associated with adjuvant therapy administration after PD at a high-volume center.

STUDY DESIGN

Preoperative and perioperative variables were reviewed in a consecutive series of 85 patients with pancreatic adenocarcinoma undergoing PD without preoperative chemotherapy or radiotherapy from 1990 to 2004.

RESULTS

Study groups included patients undergoing emergency PD (group 1, n=13); elective PD with good preoperative Eastern Cooperative Oncology Group (ECOG) performance status (PS) (group 2, ECOG PS: 0 to 1, n=63); and elective PD with marginal preoperative PS (group 3, ECOG PS: 2 to 3, n=9). Delayed recovery of PS precluded adjuvant therapy in 23% of patients in group 1, 6% of patients in group 2, and 44% of patients in group 3 (p=0.0001).

CONCLUSIONS

The impact of delayed recovery after PD on the delivery of adjuvant therapy depends on the urgency of surgery and the preoperative PS. For patients with good preoperative PS who undergo elective PD at a high-volume center, it is uncommon for delayed recovery to preclude delivery of adjuvant therapy.

Use of adjuvant radiotherapy at hospitals with and without on-site radiation services

BACKGROUND

In many areas of health care, whether patients receive specific medical interventions often is influenced heavily by the local availability of resources for delivering those services. However, relations between resource availability and utilization are relatively unexplored in cancer care, including perioperative adjuvant therapy.

METHODS

The authors studied associations between the on-site availability of radiation services and the use of adjuvant radiotherapy using the national, linked Surveillance, Epidemiology, and End Results-Medicare database (from 1992 to 2002). They examined 1 cancer for which the effectiveness of adjuvant radiotherapy was well established in randomized clinical trials (rectal cancer) and another cancer for which it was not (pancreatic cancer) (N = 10,198). The availability of on-site radiation services at the hospital where surgery was performed was assessed by using data from the American Hospital Association. In comparing rates of adjuvant radiotherapy, analyses were adjusted for both patient characteristics and other hospital attributes.

RESULTS

For rectal cancer, the use of adjuvant radiotherapy was similar in patients who underwent surgery at centers with and without on-site radiation services (29% vs 29%, respectively). Among patients with pancreatic cancer, however, those who underwent surgery at hospitals with on-site radiation services were twice as likely to receive radiotherapy than patients who underwent surgery at hospitals without such services (43% vs 26%, respectively; adjusted odds ratio, 2.1; 95% confidence interval, 1.4-3.2). Adjusting for other factors, the groups had similar survival rates for each cancer.

CONCLUSIONS

The availability of on-site radiation services significantly increased the likelihood that patients would receive radiotherapy, at least for cancers for which the effectiveness of such therapy was not well established.

Sanguinarine induces apoptosis of human pancreatic carcinoma AsPC-1 and BxPC-3 cells via modulations in Bcl-2 family proteins

Pancreatic cancer is associated with low responsiveness to conventional chemotherapies and its incidence nearly equals its death rate. This warrants the development of novel mechanism-based approaches for the management of pancreatic cancer. This study was designed to determine the potential of sanguinarine, a plant alkaloid known to possess strong antimicrobial, anti-inflammatory, and antioxidant activities, against human pancreatic carcinoma cells. Employing human pancreatic carcinoma AsPC-1 and BxPC-3 cells, we specifically evaluated the pro-apoptotic and cell cycle deregulatory effects of sanguinarine and evaluated the involvement of Bcl-2 family proteins and p53 as the mechanism of the biological effects of sanguinarine. Our data demonstrated that sanguinarine (at low concentrations of 0.1-10 microM; for 24 h) treatment to AsPC-1 and BxPC-3 cells resulted in a dose dependent (i) inhibition of viability and growth, (ii) colony formation ability, (iii) induction of apoptosis, and (iv) G0-G1 phase cell cycle arrest. Further, sanguinarine-treatment to AsPC-1 and BxPC-3 cells resulted in a dose dependent (i) increase in pro-apoptotic Bax, Bid and Bak proteins; (ii) decrease in anti-apoptotic Bcl-2 and Bcl-X(L) proteins; and (iii) decrease in p53 with an increase in its phosphorylation. Based on our study, we suggest that sanguinarine may be developed as an agent for the management of pancreatic cancer. Indeed, more in depth studies both in vitro as well as in vivo in appropriate relevant animal models are needed to strengthen this suggestion.

Gastrointestinal, Pancreatic, and Hepatic Cancer During Pregnancy

Pregnancy affects the clinical presentation, evaluation, treatment, and prognosis of patients with gastrointestinal cancer. Pregnant patients may present with advanced gastrointestinal cancer as a result of delayed diagnosis, in part because of difficulty differentiating signs and symptoms of cancer from signs and symptoms of normal pregnancy. The approach to cancer surgery and chemotherapy must be modified in pregnant patients to minimize fetal and maternal risks. Because of these factors, women who develop gastrointestinal cancers during pregnancy seem to have a poor prognosis. This article focuses on cancers of the colon, stomach, pancreas, and liver that occur during pregnancy.

Validation of a postresection pancreatic adenocarcinoma nomogram for disease-specific survival

PURPOSE

Nomograms are statistically based tools that provide the overall probability of a specific outcome. They have shown better individual discrimination than the current TNM staging system in numerous patient tumor models. The pancreatic nomogram combines individual clinicopathologic and operative data to predict disease-specific survival at 1, 2, and 3 years from initial resection. A single US institution database was used to test the validity of the pancreatic adenocarcinoma nomogram established at Memorial Sloan-Kettering Cancer Center.

PATIENTS AND METHODS

The nomogram was created from a prospective pancreatic adenocarcinoma database that included 555 consecutive patients between October 1983 and April 2000. The nomogram was validated by an external patient cohort from a retrospective pancreatic adenocarcinoma database at Massachusetts General Hospital that included 424 consecutive patients between January 1985 and December 2003.

RESULTS

Of the 424 patients, 375 had all variables documented. At last follow-up, 99 patients were alive, with a median follow-up time of 27 months (range, 2 to 151 months). The 1-, 2-, and 3-year disease-specific survival rates were 68% (95% CI, 63% to 72%), 39% (95% CI, 34% to 44%), and 27% (95% CI, 23% to 32%), respectively. The nomogram concordance index was 0.62 compared with 0.59 with the American Joint Committee on Cancer (AJCC) stage (P = .004). This suggests that the nomogram discriminates disease-specific survival better than the AJCC staging system.

CONCLUSION

The pancreatic cancer nomogram provides more accurate survival predictions than the AJCC staging system when applied to an external patient cohort. The nomogram may aid in more accurately counseling patients and in better stratifying patients for clinical trials and molecular tumor analysis.

5-fluorouracil and gemcitabine potentiate the efficacy of oncolytic herpes viral gene therapy in the treatment of pancreatic cancer

Oncolytic herpes viruses are attenuated, replication-competent viruses that selectively infect, replicate within, and lyse cancer cells and are highly efficacious in the treatment of a wide variety of experimental cancers. The current study seeks to define the pharmacologic interactions between chemotherapeutic drugs and the oncolytic herpes viral strain NV1066 in the treatment of pancreatic cancer cell lines. The human pancreatic cancer cell lines Hs 700T, PANC-1, and MIA PaCa-2 were treated in vitro with NV1066 at multiplicities of infection (MOI; ratio of the number of viral particles per tumor cell) ranging from 0.01 to 1.0 with or without 5-fluorouracil (5-FU) or gemcitabine. Synergistic efficacy was determined by the isobologram and combination-index methods of Chou and Talalay. Viral replication was measured using a standard plaque assay. Six days after combination therapy, 76% of Hs 700T cells were killed compared with 43% with NV1066 infection alone (MOI = 0.1) or 0% with 5-FU alone (2 micromol/L) (P < .01). Isobologram and combination-index analyses confirmed a strongly synergistic pharmacologic interaction between the agents at all viral and drug combinations tested (LD5 to LD95) in the three cell lines. Dose reductions up to 6- and 78-fold may be achieved with combination therapy for NV1066 and 5-FU, respectively, without compromising cell kill. 5-FU increased viral replication up to 19-fold compared with cells treated with virus alone. Similar results were observed by combining gemcitabine and NV1066. We have demonstrated that 5-FU and gemcitabine potentiate oncolytic herpes viral replication and cytotoxicity across a range of clinically achievable doses in the treatment of human pancreatic cancer cell lines. The potential clinical implications of this synergistic interaction include improvements in efficacy, treatment-associated toxicity, tolerability of therapeutic regimens, and quality of life. These data provide the cellular basis for the clinical investigation of combined oncolytic herpes virus therapy and chemotherapy in the treatment of pancreatic cancer.