Disease-free survival is not a surrogate endpoint for overall survival in adjuvant trials of pancreatic cancer: a systematic review of randomized trials

BACKGROUND

Adjuvant chemotherapy (CT) is the standard of care for patients with resected pancreatic cancer (PC). Overall survival (OS) has traditionally represented the primary endpoint in randomized trials assessing adjuvant therapies for PC. The aim of this study was to assess if disease-free survival (DFS) was an adequate surrogate endpoint for OS in randomized trials of adjuvant therapy in PC.

METHODS

A systematic literature search was conducted in PubMed, Web of Science, SCOPUS and Embase, Cochrane Library and the World Health Organization International Clinical Trials Registry Platform up to February 2nd, 2017. Surrogacy of DFS with OS was assessed between endpoints and OS through the Spearman rank correlation coefficient, and between the treatment effects on the endpoints using the squared correlation R².

RESULTS

A total of 12 eligible randomized trials that enrolled 4,888 patients where identified for the final analysis. Correlation of DFS with OS was weak at the individual level (Spearman rank correlation coefficient = 0.31) and moderate at the trial level (R² = 0.44).

CONCLUSIONS

DFS does not represent an appropriate surrogate for OS in randomized trials of adjuvant therapy for resected PC. Hence, OS should remain the primary endpoint of future trials evaluating new agents in postsurgical setting.

Randomized Clinical Trials in Pancreatic Cancer

The management of pancreatic cancer has grown rapidly in the last decade. The Gastrointestinal Tumor Study Group trial in 1985 supported postoperative chemoradiation, and a more recent study recommended 6 months of adjuvant gemcitabine and capecitabine or monotherapy with gemcitabine or fluorouracil plus folinic acid, in the absence of neoadjuvant therapy. Clinicians are now studying the role of targeted therapy in pancreatic cancer and neoadjuvant chemotherapy in resectable, borderline resectable, and locally advanced pancreatic cancer. This article critically evaluates the evolution of pancreatic cancer management, focussing on level 1a, prospective randomized control trials from 2007 to 2017.

Pancreatic Ductal Adenocarcinoma: Current and Evolving Therapies

Pancreatic ductal adenocarcinoma (PDAC), which constitutes 90% of pancreatic cancers, is the fourth leading cause of cancer-related deaths in the world. Due to the broad heterogeneity of genetic mutations and dense stromal environment, PDAC belongs to one of the most chemoresistant cancers. Most of the available treatments are palliative, with the objective of relieving disease-related symptoms and prolonging survival. Currently, available therapeutic options are surgery, radiation, chemotherapy, immunotherapy, and use of targeted drugs. However, thus far, therapies targeting cancer-associated molecular pathways have not given satisfactory results; this is due in part to the rapid upregulation of compensatory alternative pathways as well as dense desmoplastic reaction. In this review, we summarize currently available therapies and clinical trials, directed towards a plethora of pathways and components dysregulated during PDAC carcinogenesis. Emerging trends towards targeted therapies as the most promising approach will also be discussed.

3rd St. Gallen EORTC Gastrointestinal Cancer Conference: Consensus recommendations on controversial issues in the primary treatment of pancreatic cancer

The primary treatment of pancreatic cancer was the topic of the 3rd St. Gallen Conference 2016. A multidisciplinary panel reviewed the current evidence and discussed controversial issues in a moderated consensus session. Here we report on the key expert recommendations. It was generally accepted that radical surgical resection followed by adjuvant chemotherapy offers the only evidence-based treatment with a chance for cure. Initial staging should classify localised tumours as resectable or unresectable (i.e. locally advanced pancreatic cancer) although there remains a large grey-zone of potentially resectable disease between these two categories which has recently been named as borderline resectable, a concept which was generally accepted by the panel members. However, the definition of these borderline-resectable (BR) tumours varies between classifications due to their focus on either (i) technical hurdles (e.g. the feasibility of vascular resection) or (ii) oncological outcome (e.g. predicting the risk of a R1 resection and/or occult metastases). The resulting expert discussion focussed on imaging standards as well as the value of pretherapeutic laparoscopy. Indications for biliary drainage were seen especially before neoadjuvant therapy. Following standard resection, the panel unanimously voted for the use of adjuvant chemotherapy after R0 resection and considered it as a reasonable standard of care after R1 resection, even though the optimal pathologic evaluation and the definition of R0/R1 was the issue of an ongoing debate. The general concept of BR tumours was considered as a good basis to select patients for preoperative therapy, albeit its current impact on the therapeutic strategy was far less clear. Main focus of the conference was to discuss the limits of surgical resection and to identify ways to standardise procedures and to improve curative outcome, including adjuvant and perioperative treatment.

Unravelling the pharmacologic opportunities and future directions for targeted therapies in gastro-intestinal cancers Part 1: GI carcinomas

Until the 1990s, cytotoxic chemotherapy has been the cornerstone of medical therapy for gastrointestinal (GI) cancers. Better understanding of the molecular biology of cancer cell has led to the therapeutic revolution of targeted therapies, i.e. monoclonal antibodies or small molecule inhibitors directed against proteins that are specifically overexpressed or mutated in cancer cells. These agents being more specific to cancer cells were expected to be less toxic than cytotoxic agents. Targeted agents have provided clinical benefit in many GI cancer types. For example, antiangiogenics and anti-EGFR therapies have significantly improved survival of patients affected by metastatic colorectal cancer and have deeply changed the therapeutic strategy in this disease. However, their effects have sometimes been disappointing, due to intrinsic or acquired resistance mechanisms (e.g., RAS mutation for anti-EGFR therapies), or to an activity restricted to some tumour settings (e.g., lack of activity in other cancer types, or on the microscopic residual disease in adjuvant setting). Many studies are negative in overall population but positive in some specific patient subgroups (e.g., trastuzumab in HER2-positive gastric cancer), illustrating the importance of patient selection and early identification of predictive biomarkers of response to these therapies. We propose a comprehensive two-part review providing a panoramic approach of the successes and failures of targeted agents in GI cancers to unravel the pharmacologic opportunities and future directions for these agents in GI oncology. In this first part, we will focus on adenocarcinomas and squamous cell carcinomas, for which targeted therapies are mostly used in combination with chemotherapy.

Multimodal treatment of resectable pancreatic ductal adenocarcinoma

After a timing preoperative staging, treatment of resectable pancreatic adenocarcinoma (PDAC) includes surgery and adjuvant therapies, the former representing the initial therapeutic option and the latter aiming to reduce the incidence of both distant metastases (chemotherapy) and locoregional failures (chemoradiotherapy). Herein, we provide a critical overview on the role of multimodal treatment in PDAC and on new opportunities related to current more active poli-chemotherapy regimens, targeted therapies, and the more recent immunotherapy approaches. Moreover, an analysis of pathological markers and clinical features able to help clinicians in the selection of the best therapeutic strategy will be discussed. Lastly, the role of neoadjuvant treatment of initially resectable disease will be considered mostly in patients whose malignancy shows morphological but not clinical or biological criteria of resectability. Depending on the results of these investigational studies, today a multidisciplinary approach can offer the best address therapy for these patients.

Targeting the microenvironment of pancreatic cancer: overcoming treatment barriers and improving local immune responses

Historically, patients diagnosed with metastatic pancreatic cancer have faced a grim prognosis. The survival benefit seen with systemic chemotherapies and even combinations thereof have been disappointing. However, growing data suggest that the microenvironment of pancreatic cancer may be contributing to this poor prognosis. This microenvironment has a dense fibrotic stroma, and is hypoxic and highly immunosuppressive, all of which pose barriers to treatment. Newer strategies looking to disrupt the fibrotic stroma, target hypoxic areas, and improve local immune responses in the tumor microenvironment are currently undergoing clinical evaluation and seem to offer great promise. In addition to these therapies, preclinical work evaluating novel cytotoxic agents including nanoparticles has also been encouraging. While much research still needs to be done, these strategies offer new hope for patients with pancreatic cancer.

Adjuvant and Neoadjuvant Therapy for Pancreatic Cancer

Pancreas adenocarcinoma is an aggressive malignancy. The risk of recurrence remains high even for patients with localized disease undergoing surgical resection. Adjuvant systemic therapy has demonstrated the ability to reduce the risk of recurrence and prolong survival. Determination of optimal adjuvant treatment, systemic therapy, and/or combinations to further improve recurrence rates and overall survival are still needed. Neoadjuvant therapy represents an alternative emerging paradigm of investigation with several theoretic advantages over adjuvant therapy. This article summarizes the major adjuvant and neoadjuvant studies for pancreas adenocarcinoma and highlights key areas of ongoing investigation.

Adjuvant therapy for pancreas cancer in an era of value based cancer care

In resected pancreas cancer, adjuvant therapy improves outcomes and is considered the standard of care for patients who recover sufficiently post operatively. Chemotherapy or combined chemotherapy and radiation therapy (chemoradiation; CRT) are strategies used in the adjuvant setting. However, there is a lack of evidence to suggest whether the addition of RT to chemotherapy translates to an improvement in clinical outcomes. This is true even when accounting for the subset of patients with a higher risk for recurrence, such as those with R1 and lymph node positive disease. When considering the direct and indirect costs, impact on quality of life and questionable added clinical benefit, the true "net health benefit" from added RT to chemotherapy becomes more uncertain. Future directions, including the utilization of modern RT, integration of novel therapies, and intensifying chemotherapy regimens may improve outcomes in resected pancreas cancer.

State of the art and future directions of pancreatic ductal adenocarcinoma therapy

Pancreatic ductal adenocarcinoma (PDAC) is expected to become the second cause of cancer-related death in 2030. PDAC is the poorest prognostic tumor of the digestive tract, with 80% of patients having advanced disease at diagnosis and 5-year survival rate not exceeding 7%. Until 2010, gemcitabine was the only validated therapy for advanced PDAC with a modest improvement in median overall survival as compared to best supportive care (5-6 vs 3 months). Multiple phase II-III studies have used various combinations of gemcitabine with other cytotoxics or targeted agents, most in vain, in attempt to improve this outcome. Over the past few years, the landscape of PDAC management has undergone major and rapid changes with the approval of the FOLFIRINOX and gemcitabine plus nab-paclitaxel regimens in patients with metastatic disease. These two active combination chemotherapy options yield an improved median overall survival (11.1 vs 8.5 months, respectively) thus making longer survival a reasonably achievable goal. This breakthrough raises some new clinical questions about the management of PDAC. Moreover, better knowledge of the environmental and genetic events that underpin multistep carcinogenesis and of the microenvironment surrounding cancer cells in PDAC has open new perspectives and therapeutic opportunities. In this new dynamic context of deep transformation in basic research and clinical management aspects of the disease, we gathered updated preclinical and clinical data in a multifaceted review encompassing the lessons learned from the past, the yet unanswered questions, and the most promising research priorities to be addressed for the next 5 years.