Adenocarcinoma of pancreas is the fourth most common
cause of cancer-related death among U.S. men and
women. Due to lack of specific symptoms and effective
screening modality, about 80% of pancreatic cancer cases
are diagnosed at advanced stage with locally advanced
or metastatic disease. Surgical resection remains the
only curative therapy for pancreatic cancer patients, and
5-year survival for surgically resected patients is only 30%.
Therefore, more research and novel strategies are urgently
needed to understand biology better, detect the disease
sooner, and develop better treatment to improve survival
and quality of life. In this focused issue, we have covered
important topics related to biology, detection and treatment
of pancreatic cancer.
Imaging modality is important to identify patients at
risk for pancreatic cancer. With the advance of imaging
modality and technique, there has been significant
improvement in identifying smaller tumor in pancreas. At
present time, only about 15-20% of patients have resectable
disease at the time of diagnosis. Preoperative staging to
assess the extent of disease is critical to select patients for
complete (R0) resection. Besides distant metastasis, lesions
involving superior mesenteric artery and/or celiac axis are
generally considered unresectable. Pre-operative evaluation
with computed tomography and other modality such as
endoscopic ultrasound can better select patients for R0
resection. Tummala et al. have reviewed different imaging
modalities and their utility in assessing patients with
suspicious pancreatic lesion, and identifying unresectable
disease in patients with pancreatic cancer (
1).
The improvement in perioperative care and surgical techniques has led to decrease in mortality and morbidity
for patients receiving resection of pancreatic cancer. Kim
and colleagues have reviewed the surgical management
including preoperative evaluation, different surgical
techniques including minimally invasive surgery and
advances in perioperative care (
2). Furthermore, they have
discussed the recent consensus definition of borderline
resectable disease, which has emerged as a unique entity
with active clinical investigation.
Chemotherapy and chemoradiation (CRT) a retreatment options for resected pancreatic cancer as
adjuvant treatment, and as primary treatment for locally
advanced disease not amenable for resection. There is no
standard neoadjuvant treatment for patients with resectable
or borderline resectable disease. Clinical studies using
chemotherapy followed by CRT as neoadjuvant treatment
in locally advanced disease have demonstrated benefits
in converting borderline resectable to resectable disease.
Varadhachary has provided a thorough review of the staging
systems for borderline resectable lesions, rationale and
clinical investigation of preoperative therapies, and the
utility of predictive biomarkers (
3).
Less than half of pancreatic cancer patients in U.S.A.
are being referred to high-volume centers for surgery
(
4). Many reports have shown pancreatic cancer patients
undergoing surgery have better outcomes at high-volume
hospitals, and National Comprehensive Cancer Network
(NCCN) recommends resection to be done in a center
with more than 15-20 resection experience annually
(
5-7). Moreover, regardless the volume of the hospital,
the surgeon experience seems to contribute most to the
outcome of patients receiving pancreatic surgery (
8). Cheng
and colleagues of a multidisciplinary team in a community
hospital have reported a similar outcome of pancreatic
surgery compared to published results from high-volume
centers (
9). This echoes the importance of multidisciplinary
approach and experienced surgeon in managing pancreatic
cancer.
Adjuvant chemotherapy with gemcitabine or
5-fluorouracil has been shown in several large randomized studies to significantly increase the 5-year survival (from
approximately 10 to 20%), and should be offered if the
patient is fit after surgery (
10-12). Adjuvant CRT is a heavily
debated topic, with practices in U.S.A. often favoring the use
of this adjuvant approach, but not recommended in Europe
to lack of any randomized study to show survival benefit
of this strategy (
7,
13). For locally advanced pancreatic
cancer not amenable for resection, the treatment options
could either be chemotherapy alone or chemotherapy in
conjunction with CRT. By using advanced radiotherapy
modalities such as intensity modulation and stereotactic
body radiation therapy, the toxicity of radiotherapy could be
reduced and dose escalation of radiation becomes possible
to improve locoregional control. Wang and Kumar have
presented an excellent review on the historic evolution
of CRT, and the application of modern radiotherapy
modalities in the treatment of pancreatic cancer (
14).
Gemcitabine has become the standard therapy for
advanced pancreatic cancer since its approval more than
a decade ago. Subsequent investigational strategies have
included the addition of targeted or other cytotoxic agents
to gemcitabine, and all yielded disappointing results except
2-week gain of survival by adding erlotinib to gemcitabine
(
15). The addition of other targeted agent such as cetuximab
or bevacizumab to gemcitabine, on the other hand did not
result in any survival improvement (
16). The combination
of 5-f luorouracil, leucovorin, irinotecan, and oxaliplatin
(FOLFIRINOX) has shown improved overall survival by 4
to 5 months vs. gemcitabine in a phase III study involving
more than 340 patients with metastatic pancreatic cancer
(
17). FOLFIRINOX has become a new standard for patients
with advanced pancreatic cancer, as recommended by
NCCN; this regimen should be used with caution due to
significant toxicities and lack of safety data in patients with
suboptimal performance status. Nevertheless, identification
of novel pathways and incorporating novel targeted agents
to standard regimen are the continuing efforts of research
to advance the treatment (
18).
Emerging data have indicated epithelial-mesenchymal
transition (EMT) plays important role in the development
and progression of pancreatic adenocarcinoma. During
EMT, cancer cells shed off epithelial characteristics and
pick up properties of mesenchymal cells with increased
motility and invasiveness. Therefore EMT of pancreatic
cancer may provide a promising novel target for therapeutic
development. Pan and Yang have rev iewed EMT of
pancreatic cancer with involved signal transduction
pathways and its therapeutic implications (
19).
Nanomedicines are pharmaceuticals prepared by
manipulating matter at the nanoscale (< 1000 nm); i.e.
manipulations at less than 1000th of a millimeter. The vast majority of nanomedicines are the result of the
packaging of pharmacologically active compounds within
nanovectors (5 ~ 800 nm). Nanovector formulations have
several advantages over conventional chemotherapy:
protecting drugs from being degraded in the body before
they reach their target, enhancing uptake of drugs into
tumor, allowing for better control over the timing and
distribution of drugs to tumor tissue, and preventing drugs
from interacting with normal cells thus decreasing the
toxicities. In this issue, Tsai et al. present a comprehensive
review of nanovector-based therapies in patients with
advanced pancreatic cancer (
20).
Palliative care is an important part of treatment for
patients with advanced pancreatic cancer. Pain is frequently
reported by patients with advanced disease, and about
10 to 15% of patients have inadequate pain control with
routine management (
21). Pain syndromes are mainly due
to the proximity of pancreas to a number of other critical
structures: the duodenum, liver, stomach, jejunum, and
transverse colon. In this issue, Khokhlova and Hwang
present the rationale and data of high intensity focused
ultrasound (HIFU), a novel non-invasive ablation modality,
for palliative treatment of pancreatic cancer (
22). HIFU
delivers ultrasound energy from an extracorporeal source to
tumor, and causes thermal damages of tumor tissue at the
focus without affecting surrounding organs.
Although the treatment of pancreatic cancer remains
a daunting task, it is entering a new avenue with the
development of novel strategies, innovative trials and
multidisciplinary approach. Additionally, identification
of prognostic and predictive markers can personalize
treatment and select patients for target-driven therapy.
Collaborative efforts have been put into action to facilitate
the translation of bench research to bedside study (
23,
24).
We should anticipate progress beyond baby steps in the nottoo-
distant future.