Faculty Bibliography

Sonic hedgehog (Shh), a soluble ligand overexpressed by neoplastic cells in pancreatic ductal adenocarcinoma (PDAC), drives formation of a fibroblast-rich desmoplastic stroma. To better understand its role in malignant progression, we deleted Shh in a well-defined mouse model of PDAC. As predicted, Shh-deficient tumors had reduced stromal content. Surprisingly, such tumors were more aggressive and exhibited undifferentiated histology, increased vascularity, and heightened proliferation--features that were fully recapitulated in control mice treated with a Smoothened inhibitor. Furthermore, administration of VEGFR blocking antibody selectively improved survival of Shh-deficient tumors, indicating that Hedgehog-driven stroma suppresses tumor growth in part by restraining tumor angiogenesis. Together, these data demonstrate that some components of the tumor stroma can act to restrain tumor growth.

No common malignancy is as rapidly and inevitably fatal as pancreatic ductal adenocarcinoma (PDA). This grim fact has driven substantial research efforts into this disease in recent decades. Unfortunately, the investment has yet to result in a meaningful increase in 5-year survival. This has prompted many pancreatic cancer researchers and advocates to redouble their efforts, but also requires one to step back and ask why the previous efforts were lacking and to consider why pancreatic cancer is so difficult to treat. The difficulties are legion. PDA is characterized by an insidious clinical syndrome, but is rarely diagnosed at a time when surgical resection is feasible. We lack markers of early detection and screening programs remain unproven even in high risk populations. The location of the tumor in the retroperitoneum, the advanced age of patients, and the systemic effects of disease limit the options for local therapy. Chemotherapy may provide a small benefit, but most efforts to improve on the current regimens consistently and stubbornly fail in advanced clinical trials. The molecular and cellular features of ductal pancreatic tumors are aggressive and underlay multiple levels of therapeutic resistance. Non-cell-autonomous features including stromal proliferation, reduced vascular density and immune suppression also contribute to therapeutic resistance. Growing awareness of these the fundamental features of PDA has begun to guide ongoing research efforts. Clinical trials are now specifically targeting these tumor properties and actively focusing on the therapeutic implications of tumor stroma. As reviewed here, reflecting on the fundamental question of why pancreatic cancer is so difficult to treat is a necessary and informative exercise that will aid our efforts to improve patient outcomes. These efforts will lead to improvements in clinical trial design, expand our focus to include the molecular and histologic implications of novel treatment paradigms, and ultimately change the lives of our patients.

Gemcitabine was approved for advanced pancreatic cancer in 1996. We investigated uptake and predictors of its use. We identified 3,231 individuals > 65 years in the SEER-Medicare database with stage IV pancreatic adenocarcinoma, diagnosed between 1998-2005, who survived > 30 days. Of these, 54% received chemotherapy, 93% with gemcitabine. Gemcitabine nonreceipt was associated with advanced age and unmarried (OR: 0.65, 95% CI: 0.55-0.76). Diagnosis in 2004-2005 versus 1998-2000 was more likely to receive gemcitabine (OR: 1.51, 95% CI: 1.23-1.84) as were higher SES patients (highest versus lowest quintile, OR: 2.14, 95% CI: 1.60-2.85). Gemcitabine was rapidly adopted among elderly advanced pancreatic cancer patients; several factors are associated with use.

 Neuroendocrine tumors (NETs) describe a heterogeneous group of tumors with a wide range of morphologic, functional, and behavioral characteristics. Pancreatic neuroendocrine tumors (pNET) are a subset of NETs which are increasing in incidence and prevalence. These tumors are generally slow growing and behave in an indolent fashion. However, when these tumors spread they can be life threatening and difficult to treat with current modalities. In 2011, the landscape of treatment for pNET was changed with the approval of two targeted agents, sunitinib and everolimus, the first new therapies for this disease in over 20 years. Data from these clinical trials and extensive preclinical work into the underlying molecular pathways in neuroendocrine tumors has generated intense interest in the quest to identify additional effective agents in this challenging disease. At the 2012 American Society of Clinical Oncology (ASCO) Annual Meeting, several researchers presented updated data regarding the use of targeted agents, alternative chemotherapeutic agents and combinations of these in the treatment of pNET. Corrie et al. (Abstract #4121) reported data from a chemotherapy clinical trial replacing 5-FU with capecitabine and evaluating the addition of cisplatin in NETs. Several authors reviewed the addition of the anti VEGF monoclonal antibody bevacizumab into combination therapy. Ducreux et al (Abstract #4036) presented results from a trial of chemotherapy plus bevacizumab while Firdaus et al. (Abstract #4127) reported the results of combination therapy with octreotide, bevacizumab, and pertuzumab. Hobday et al. (Abstract #4048) reported positive results of an interim analysis of combination therapy with an mTOR inhibitor and bevacizumab. Kulke et al (Abstract #4125) reported the results of a clinical trial utilizing an antibody targeting the insulin growth factor receptor. Finally, Vinik et al. (Abstract #4118) provided updated survival data form the seminal phase III trial that led to approval of sunitinib in the treatment of pNET. The authors review and summarize these abstracts in this article. 

Neuroendocrine tumors (NETs) describe a heterogeneous group of tumors with a wide range of morphologic, functional, and behavioral characteristics. These tumors are often indolent but they have the potential to cause symptoms through release of hormones and through local or distant spread. Pancreatic neuroendocrine tumors (pNET) represent a subset of NETs and they have a unique pattern of symptoms and disease progression. Due to the heterogeneity of this disease it is important to identify reliable markers to help guide prognosis and predict response to therapy. The recent approval of two new agents in the treatment of advanced pNET has raised additional interest in the significance of molecular markers in this disease. At the 2012 American Society of Clinical Oncology (ASCO) Annual Meeting, several investigators reported on collaborative efforts to develop clinically useful biomarkers for this disease. Choti et al. (Abstract #4126) reported data about the functional characteristics of NETs and pNETs among a multi-institutional cohort finding that a substantial minority of patients have functional symptoms even when the disease is localized. Faggiano et al. (Abstract #1604) looked at a wide spectrum of NETs in several referral centers and reported on predictors of both short term and long term survival in this setting. Yao et al. (Abstract #4014) reported analysis of predictive biomarkers among patients in the RADIANT-2 trial which looked at the role of the mTOR inhibitor, everolimus compared to placebo in NET. Fischer et al. (Abstract #4128) looked at a novel biomarker, placental growth factor (PlGF) and evaluated the role of serum and tissue levels of this protein as a predictive marker. Finally, Khan et al. (Abstract #4123) investigated the role of circulating tumor cells in NET (and pNET) and found that this may have potential as a prognostic marker and an early marker of response to therapy. The authors review and summarize these abstracts in this article.