Stereotactic Body Radiation Therapy for Locally Advanced Pancreatic Cancer: A Systematic Review and Pooled Analysis of 19 Trials

Phase I trial of concurrent stereotactic body radiotherapy and nelfinavir for locally advanced borderline or unresectable pancreatic adenocarcinoma

INTRODUCTION

The HIV protease inhibitor nelfinavir (NFV) displays notable radiosensitizing effects. There have been no studies evaluating combined stereotactic body radiotherapy (SBRT) and NFV for borderline/unresectable pancreatic cancer. The primary objective of this phase I trial (NCT01068327) was to determine the maximum tolerated SBRT/NFV dose, and secondarily evaluate outcomes.

METHODS

Following initial imaging, pathologic confirmation, and staging laparoscopy, subjects initially received three 3-week cycles of gemcitabine/leucovorin/fluorouracil; patients without radiologic progression received 5-fraction SBRT/NFV. Dose escalation was as follows: (1) 25 Gy/625 mg BID ×3wks; (2) 25 Gy/1250 mg BID ×3wks; (3) 30 Gy/1250 mg BID ×3wks; (4) 35 Gy/1250 mg BID ×3wks; (5) 35 Gy/1250 mg BID ×5wks; and (6) 40 Gy/1250 mg BID ×5wks. Pancreaticoduodenectomy was performed thereafter if resectable; if not, gemcitabine/leucovorin/fluorouracil was administered.

RESULTS

Forty-six patients enrolled (10/2008-5/2013); 39 received protocol-directed therapy. Sixteen (41%) experienced any grade ≥2 event during and 1 month after SBRT. Four grade 3 and both grade 4 events occurred in a single patient at the initial dose level. 40 Gy/1250 mg BID ×5wks was the maximum tolerated dose. Five patients had late gastrointestinal bleeding (n = 2 superior mesenteric artery pseudo-aneurysm, n = 1 disease progression, n = 1 lower GI tract, n = 1 unknown location). The median overall survival was 14.4 months. Six (15%) patients recurred locally; median local failure-free survival was not reached. The median distant failure-free survival was 11 months, and median all failure-free survival was 10 months.

CONCLUSIONS

Concurrent SBRT (40 Gy)/NFV (1250 mg BID) for locally advanced pancreatic cancer is feasible and safe, although careful attention to treatment planning parameters is recommended to reduce the incidence of late gastrointestinal bleeding.

Review and current state of radiation therapy for locally advanced pancreatic adenocarcinoma

Pancreatic cancer is characterized by a high rate of metastatic spread and overall poor prognosis. Yet 30% of patients have progressive local disease at the time of death, and local progression can cause significant morbidity. Approximately 30-40% of patients present with locally advanced pancreatic cancer (LAPC) that is not surgically resectable, and the optimal treatment for these patients continues to evolve. The role of radiation in the management of LAPC is an area of controversy, and the recent LAP07 randomized trial reported no survival benefit of radiation following gemcitabine plus or minus erlotinib. However, the efficacy of modern systemic regimens has improved since the design of the LAP07 study, and radiation therapy may be of greater benefit in the context of more effective systemic therapy. Advances in radiation delivery including the increasing use of stereotactic body radiation therapy (SBRT) have the potential to improve outcomes through dose escalation and better treatment tolerability. In addition, the combination of radiation therapy and immune therapy is an area of promising research. These advances suggest that radiation therapy will continue to play an integral role in the management of LAPC.

Comparison of different treatment planning approaches for intensity-modulated proton therapy with simultaneous integrated boost for pancreatic cancer

BACKGROUND

Neoadjuvant radio(chemo)therapy of non-metastasized, borderline resectable or unresectable locally advanced pancreatic cancer is complex and prone to cause side-effects, e.g., in gastrointestinal organs. Intensity-modulated proton therapy (IMPT) enables a high conformity to the targets while simultaneously sparing the normal tissue such that dose-escalation strategies come within reach. In this in silico feasibility study, we compared four IMPT planning strategies including robust multi-field optimization (rMFO) and a simultaneous integrated boost (SIB) for dose-escalation in pancreatic cancer patients.

METHODS

For six pancreatic cancer patients referred for adjuvant or primary radiochemotherapy, four rMFO-IMPT-SIB treatment plans each, consisting of two or three (non-)coplanar beam arrangements, were optimized. Dose values for both targets, i.e., the elective clinical target volume [CTV, prescribed dose D_pres = 51Gy(RBE)] and the boost target [D_pres = 66Gy(RBE)], for the organs at risk as well as target conformity and homogeneity indexes, derived from the dose volume histograms, were statistically compared.

RESULTS

All treatment plans of each strategy fulfilled the prescribed doses to the targets (D_{pres(GTV,CTV)} = 100%, D_{95%,(GTV,CTV)} ≥ 95%, D_2%,(GTV,CTV) ≤ 107%). No significant differences for the conformity index were found (p > 0.05), however, treatment plans with a three non-coplanar beam strategy were most homogenous to both targets (p < 0.045). The median value of all dosimetric results of the large and small bowel as well as for the liver and the spinal cord met the dose constraints with all beam arrangements. Irrespective of the planning strategies, the dose constraint for the duodenum and stomach were not met. Using the three-beam arrangements, the dose to the left kidney could be significant decreased when compared to a two-beam strategy (p < 0.045).

CONCLUSION

Based on our findings we recommend a three-beam configuration with at least one non-coplanar beam for dose-escalated SIB with rMFO-IMPT in advanced pancreatic cancer patients achieving a homogeneous dose distribution in the target while simultaneously minimizing the dose to the organs at risk. Further treatment planning studies on aspects of breathing and organ motion need to be performed.

[Role of radiation therapy in the management of pancreatic cancer]

At diagnosis, about 15% of patients with pancreatic cancer present with a resectable tumour, 50% have a metastatic tumour, and 25% a locally advanced tumor (non-metastatic but unresectable due to vascular invasion) or borderline resectable. Despite the technical progress made in the field of radiation therapy and the improvement of the efficacy of chemotherapy, the prognosis of these patients remains very poor. Recently, the role of radiation therapy in the management of pancreatic cancer has been much debated. This review aims to evaluate the role of radiation therapy for these patients.

Irreversible Electroporation in pancreatic ductal adenocarcinoma: Is there a role in conjunction with conventional treatment?

BACKGROUND

The incidence of pancreatic ductal adenocarcinoma (PDAC) is rapidly increasing. Up to 30% of patients present with locally advanced disease and therefore are not candidates for surgery. Locally advanced pancreatic cancer (LAPC) is an emerging entity lacking in level III evidence-based recommendations for its treatment. Currently, systemic chemotherapy is the main treatment for LAPC. However, due to lack of response or disease progression, downsizing of the tumour, making it resectable is successful in only a small proportion of patients. Radiotherapy is often advocated to improve local disease control if there is stability following chemotherapy. Recently, Irreversible Electroporation (IRE), a novel non-thermal ablation technique, has been proposed for the treatment of LAPC.

AIMS AND METHODS

This narrative review aims to explore the potential role and timing for the use of IRE in patients with LAPC.

RESULTS

To date, there is limited and inconsistent level I and II evidence available in the literature regarding the use of IRE for the treatment of PDAC.

DISCUSSION

Although some of the preliminary experience of the use of IRE in patients with LAPC is encouraging, it should only be used after conventional evidence-based treatments and/or within the research context.

Blocking Cyclin-Dependent Kinase 4/6 During Single Dose Versus Fractionated Radiation Therapy Leads to Opposite Effects on Acute Gastrointestinal Toxicity in Mice

PURPOSE

The delivery of radiation therapy to cure gastrointestinal (GI) cancers is often limited by normal tissue toxicity of the GI tract. Studies using genetically engineered mice have demonstrated an essential role of the cyclin-dependent kinase inhibitor p21 in protecting against GI acute radiation syndrome (GI-ARS). Here, we examined the impact of the Food and Drug Administration-approved, selective, cyclin-dependent kinase 4/6 inhibitor palbociclib (PD-0332991) on the development of GI-ARS induced by single-dose versus fractionated radiation in mice.

METHODS AND MATERIALS

For the single-dose radiation study, C57BL/6J mice were treated with palbociclib or vehicle 28 and 4 hours before subtotal body irradiation (SBI). For the fractionated radiation study, C57BL/6J mice were exposed to fractionated SBI for 5 consecutive days. These mice were treated with palbociclib or vehicle either 28 and 4 hours before the first dose of irradiation or 4 hours before the first, third, and fifth doses of irradiation.

RESULTS

Our data indicate that treatment with palbociclib before, but not after, a single fraction of SBI significantly ameliorated GI-ARS, improved the integrity of the GI barrier, and increased the number of surviving crypts in the small intestine. In addition, palbociclib did not protect tumor cell lines from radiation in vitro. In contrast to the results from the single-dose exposure, treatment with palbociclib before 5 daily fractions of SBI did not prevent GI-ARS. Moreover, we unexpectedly observed that GI-ARS was exacerbated in mice treated with palbociclib before and during 5 daily fractions of SBI.

CONCLUSIONS

Our results demonstrate that treatment with palbociclib before a single dose of SBI protects mice from GI-ARS. In contrast, treatment with palbociclib before and during 5 daily fractions of SBI exacerbates GI-ARS in mice. These results emphasize the importance of conducting preclinical studies of radioprotectors with single-dose and fractionated radiation therapy.

Inhibition of PI3K/AKT Signaling Pathway Radiosensitizes Pancreatic Cancer Cells with ARID1A Deficiency in Vitro

Pancreatic cancer is among the most aggressive human cancers, and is resistant to regular chemotherapy and radiotherapy. The AT-rich interactive domain containing protein 1A (ARID1A) gene, a crucial chromatin remodeling gene, mutates frequently in a broad spectrum of cancers, including pancreatic cancer. Recent evidence suggests that ARID1A acts as tumor suppressor and plays an important role in DNA damage repair (DDR). However, the effect of ARID1A on the radiosensitivity of pancreatic cancer remains unclear. Herein, we investigated the involvement of ARID1A depletion in the radioresistance of pancreatic cancer cells, and explored the underlying mechanisms. The results reveal that knockdown of ARID1A enhances the radioresistance of pancreatic cancer cells through suppressing apoptosis, impairing G2-M checkpoint arrest, strengthening DDR, and accompanying activation of PI3K/AKT signaling pathway. Moreover, upon inhibition of PI3K/AKT pathway by PI3K-inhibitor LY294002 or AKT-inhibitor mk2206, the radiosensitivity of ARID1A-deficient pancreatic cancer cells is improved in vitro via increased apoptosis and weakened DDR. Taken together, these data suggest that loss of ARID1A expression enhances radioresistance of pancreatic cancer through activation of PI3K/AKT pathway, which maybe a promising target for radiosensitization of ARID1A-deficient pancreatic cancer.

Duodenal invasion by pancreatic adenocarcinoma: MDCT diagnosis of an aggressive imaging phenotype and its clinical implications

Despite advances in oncologic and imaging technology, pancreatic ductal adenocarcinoma remains a highly deadly disease. The only curative option, pancreaticoduodenectomy or pancreatectomy, carries a significant morbidity. Current imaging plays a role in pre-operative staging to determine the probability of achieve disease-free margins. However, a small but not insignificant number of pancreatic cancers have a relatively higher aggressive biology, despite being resectable based on traditional criteria. Recently, imaging biomarkers that serve as a surrogate for tumors with such aggressive phenotype have been described. These include duodenal invasion and extrapancreatic perineural invasion. This review will focus on the former highlighting the summary of literature supporting duodenal invasion as a surrogate for aggressive disease as well as review its MDCT imaging features.

Locally Advanced Pancreatic Cancer: A Review of Local Ablative Therapies

Pancreatic cancer is typically characterized by its aggressive tumor growth and dismal prognosis. Approximately 30% of patients with pancreatic cancer present with locally advanced disease, broadly defined as having a tumor-to-artery interface >180°, having an unreconstructable portal vein or superior mesenteric vein and no signs of metastatic disease. These patients are currently designated to palliative systemic chemotherapy, though median overall survival remains poor (approximately 11 months). Therefore, several innovative local therapies have been investigated as new treatment options for locally advanced pancreatic cancer (LAPC). This article provides an overview of available data with regard to morbidity and oncological outcome of novel local therapies for LAPC.

Stereotactic Body Radiation Therapy in the Management of Upper GI Malignancies

The role of external beam radiation therapy (EBRT) in the management of upper gastrointestinal malignancies is constantly evolving. As radiation therapy techniques improve and are able to deliver more ablative doses of radiotherapy while sparing healthy tissue, radiation can be applied to a wider range of clinical scenarios. Stereotactic body radiation therapy (SBRT) allows a high dose of radiation to be delivered to a highly conformal treatment volume in a short amount of time. Another potential advantage of SBRT is its ability to increase tumor immunogenicity, while also having less of an immunosuppressive effect on the patient, as compared to conventionally fractionated radiation therapy. In so doing, SBRT may potentiate the effects of immune therapy when the two treatments are combined, thus improving therapeutic outcomes. This article provides an overview of the role of SBRT in the management of upper gastrointestinal GI malignancies and the emerging data on immune biomarkers and SBRT, with a focus on pancreatic and liver cancer.

Potential dosimetric benefits of adaptive tumor tracking over the internal target volume concept for stereotactic body radiation therapy of pancreatic cancer

BACKGROUND

Radiotherapy for pancreatic cancer has two major challenges: (I) the tumor is adjacent to several critical organs and, (II) the mobility of both, the tumor and its surrounding organs at risk (OARs). A treatment planning study simulating stereotactic body radiation therapy (SBRT) for pancreatic tumors with both the internal target volume (ITV) concept and the tumor tracking approach was performed. The two respiratory motion-management techniques were compared in terms of doses to the target volume and organs at risk.

METHODS AND MATERIALS

Two volumetric-modulated arc therapy (VMAT) treatment plans (5 × 5 Gy) were created for each of the 12 previously treated pancreatic cancer patients, one using the ITV concept and one the tumor tracking approach. To better evaluate the overall dose delivered to the moving tumor volume, 4D dose calculations were performed on four-dimensional computed tomography (4DCT) scans. The resulting planning target volume (PTV) size for each technique was analyzed. Target and OAR dose parameters were reported and analyzed for both 3D and 4D dose calculation.

RESULTS

Tumor motion ranged from 1.3 to 11.2 mm. Tracking led to a reduction of PTV size (max. 39.2%) accompanied with significant better tumor coverage (p<0.05, paired Wilcoxon signed rank test) both in 3D and 4D dose calculations and improved organ at risk sparing. Especially for duodenum, stomach and liver, the mean dose was significantly reduced (p<0.05) with tracking for 3D and 4D dose calculations.

CONCLUSIONS

By using an adaptive tumor tracking approach for respiratory-induced pancreatic motion management, a significant reduction in PTV size can be achieved, which subsequently facilitates treatment planning, and improves organ dose sparing. The dosimetric benefit of tumor tracking is organ and patient-specific.

Stereotactic body radiotherapy for locally-advanced unresectable pancreatic cancer-patterns of care and overall survival

BACKGROUND

Unresectable pancreatic cancer remains a challenging disease to treat. Stereotactic body radiotherapy (SBRT) allows for a higher biologically equivalent dose in an abbreviated course more convenient for patients and the integration of systemic therapy. We sought to investigate utilization trends and survival outcomes for patients treated with pancreatic SBRT versus conventionally fractionated radiotherapy (CFRT).

METHODS

We engaged the National Cancer Database (NCDB) from 1998-2012 and identified locally-advanced unresectable patients with histologically confirmed, non-metastatic, pancreatic adenocarcinoma who received radiotherapy. Patients who received CFRT (1.5-4.0 Gy per fraction to a dose of ≥45 Gy, n=11,879) were compared to those who received SBRT (6-15 Gy per fraction to a dose of ≥20 Gy, n=474).

RESULTS

Median follow-up was 11.0 months (18.4 months for survivors). SBRT utilization increased from 0.2% to 7.4% from 1998 to 2012 (P<0.05). On multivariable analysis, factors predictive for preferential utilization of SBRT over CFRT were later year of diagnosis, age ≥75 years, increased facility volume, and no chemotherapy in the initial treatment plan. Unadjusted median survival was 11.2 months for CFRT vs. 12.6 months for SBRT (P=0.002). Results were consistent in the propensity matched model. Variables predictive for improved survival on multivariable analysis were diagnosis after 2010, younger age, lower comorbidity score, tumor size <3 cm, nodal stage zero, and receipt of chemotherapy (P<0.05).

CONCLUSIONS

SBRT utilization has increased significantly and is associated with a small absolute improvement in overall survival (OS) compared to CFRT. The decreased treatment time, without apparent compromise in survival, makes SBRT an attractive option for patients with unresectable pancreatic cancer warranting further research.

Synergistic effect of a drug loaded electrospun patch and systemic chemotherapy in pancreatic cancer xenograft

Pancreatic cancer has a high rate of local recurrence and poor prognosis even with adjuvant chemotherapy after curative resection. The aim of this study was to investigate if local drug delivery combined with low dose systemic chemotherapy can increase the therapeutic effect of chemotherapy while reducing systemic toxicities. Poly-L-lactic acid-based 5-FU releasing patch was fabricated by electrospinning, and its tumour killing effects were first confirmed in vitro. The 5-FU patch directly adhered to the tumour in subcutaneous and orthotopic murine models, and induced a significant decrease in tumour size. Systemic gemcitabine treatment group, 5-FU drug releasing patch group, and systemic gemcitabine plus 5-FU patch group were compared by tumour size measurement, non-invasive bio-imaging, and histology in subcutaneous models. Combination of local drug patch and systemic chemotherapy led to increased tumour suppression effects that lasted longer, as well as increased survival rate. Histology revealed higher degree of apoptosis in the combined group. Systemic toxicity was recovered within 7 days after the treatment in all mice. Conclusively, local drug delivery using biocompatible polymer patch significantly inhibited tumour growth, and combination with systemic chemotherapy was more effective than single systemic chemotherapy.

Comparison of proton beam radiotherapy and hyper-fractionated accelerated chemoradiotherapy for locally advanced pancreatic cancer

OBJECTIVES

We compared the clinical outcomes of proton beam radiotherapy (PBRT) and those of conventional chemoradiotherapy via hyper-fractionated acceleration radiotherapy (HART) after induction chemotherapy in patients with locally advanced pancreatic cancer (LAPC).

METHODS

Twenty-five consecutive patients with LAPC received induction chemotherapy comprising gemcitabine and S-1 before radiotherapy. Of these, 15 and 10 were enrolled in the HART and PBRT groups, respectively.

RESULTS

Moderate hematological toxicities were observed only in the HART group, whereas two patients in the PBRT group developed duodenal ulcers. All patients underwent scheduled radiotherapy, with overall disease control rates of 93% and 80% in the HART and PBRT groups, respectively. Local progression was observed in 60% and 40% of patients in the HART and PBRT groups, respectively. However, there was no statistical significance between the two groups regarding the median time to progression (15.4 months in both) and the median overall survival (23.4 v.s. 22.3 months).

CONCLUSIONS

PBRT was feasible and tolerable, and scheduled protocols could be completed with careful attention to gastrointestinal ulcers. Despite the lower incidence of local recurrence, PBRT did not yield obvious progression control and survival benefits relative to conventional chemoradiotherapy.

Integration of Stereotactic Body Radiation Therapy into the Multidisciplinary Management of Pancreatic Cancer

Although most patients with pancreatic cancer die of metastatic disease, an autopsy study showed that up to one-third of patients die of predominantly local disease. This patient population stands to benefit the most from radiation, surgery, or both. Unfortunately, however, single-agent chemotherapy has had minimal benefit in pancreatic cancer, and most patients progress distantly before receiving radiation therapy (RT). With the addition of multiagent chemotherapy, patients are living longer, and RT has emerged as an important modality in preventing local progression. Standard chemoradiation delivered over 5-6 weeks has been shown to improve local control, but this approach delays full-dose systemic therapy and increases toxicity when compared to chemotherapy alone. Stereotactic body RT (SBRT) delivered in 3-5 fractions can be used to accurately target the pancreatic tumor with small margins and limited acute treatment-related toxicity. Given the favorable toxicity profile, SBRT can easily be integrated with other therapies in all stages of pancreatic cancer. However, future studies are necessary to determine optimal dose or fractionation regimens and sequencing with targeted therapies and immunotherapy. The purpose of this review is to discuss our current understanding of SBRT in the multidisciplinary management of patients with pancreatic cancer and future implications.