LETTERS
K-ras Mutations in the
Plasma Correspond to
Computed Tomographic
Findings in Patients With
Pancreatic Cancer
To the Editor:
he prognosis of pancreatic carcinoma
has not improved in the past 20 years.
Despite the recent advances in diagnostic
techniques, it remains difficult to diagnose
this devastating disease in the early stage.
Developing informative noninvasive cancer biomarkers is essential to achieve early
detection of tumors to better stratify patients’ prognosis and to optimize therapy
for individual patients with cancer. Unique
to pancreatic adenocarcinoma is the high
incidence of Kirsten rat sarcoma (K-ras)
mutations reported (approximately 95%).
Patients with pancreatic ductal adenocarcinoma shed cells that harbor K-ras mutations and circulate in the peripheral blood.
We recently established a real-time polymerase chain reaction (PCR) assay with
mutant-specific hybridization probes combined with peptide nucleic acid (PNA)mediated PCR clamping of the wild-type
alleles to identify K-ras codon 12-point
mutations in plasma samples of patients
with pancreatic cancer and acute myeloid
leukemia. We demonstrated that this reliable and fast method allows quantitative
detection of altered alleles with a very high
sensitivity (1:100,000, mutated to wild-type
alleles) and might provide diagnostic and
prognostic information to physicians, especially when combined with determination of serum cancer-associated antigen
19-9 (CA 19-9). Here, we extend our previous findings by showing that K-ras
mutations in the plasma correspond to
computed tomographic (CT) findings in
patients with pancreatic cancer and provide further evidence that K-ras mutation
analysis in plasma is useful for detection
and prognostic evaluation of pancreatic
carcinoma.
T
RESULTS AND DISCUSSION
The diagnosis of pancreatic cancer
is typically made radiographically, and
contrast-enhanced CT scanning is the preferred method to diagnose and stage pancreatic cancer. In addition, several serum
markers for pancreatic cancer have been
evaluated, the most useful of which is
CA 19-9. Owing to limited sensitivity and
Pancreas
&
TO THE
EDITOR
specificity, CA 19-9 is not recommended
as a screening test for pancreatic cancer.
However, serial monitoring of CA 19-9
levels is useful to follow patients after
potentially curative surgery and for those
who are receiving chemotherapy for advanced disease. Therefore, rising CA 19-9
levels usually precede the radiographic
appearance of recurrent disease, but confirmation of disease progression should be
pursued with imaging studies and/or biopsy. In this regard, the addition of molecular genetic analysis may improve
sensitivity and may be helpful in the diagnostic evaluation for pancreatic masses at
initial presentation and in particular during the clinical follow-up setting.
Pancreatic cancer is unique in its high
frequency of K-ras mutations. Because of
the inherent difficulties in obtaining pancreatic tumor tissue for molecular analysis, detection of K-ras mutations in the
plasma DNA might provide physicians
with prognostic information of a patient
with pancreatic cancer. It has been established that 80% of tumors shed cell-free
DNA into blood1 and that the correspondence of K-ras mutations in the pancreatic
cancer tissue and circulating plasma DNA
is almost equal.2 Previous studies have
also reported that 35% to 81% of K-ras
mutations were detected in plasma of patients with pancreatic cancer 3 and showed
that the sensitivity was from 27% to 81%.2
In addition, it has been shown that K-ras
mutation in plasma DNA is a predictive
biomarker for a poor prognosis of patients
with pancreatic cancer.2,4 Therefore, the
disposition of blood-borne tumor mutations, detectable in plasma, may provide
additional insight into a patient’s response
to therapy and could potentially be used as
an early indicator of tumor recurrence.
In fact, our previously published data
indicate that the occurrence or absence of
K-ras mutations in the peripheral blood
of patients with pancreatic cancer might
reflect different tumor stages in a patient,
depending on the time of observation, indicating that the detection of K-ras mutations in plasma could reflect the tumor
burden of individual patients with pancreatic cancer.5 To evaluate the use of
plasma K-ras analysis as a marker for the
course of disease, we correlated the presence of mutated K-ras in the plasma
of patients with pancreatic cancer with
CT findings and the conventional tumor
marker CA 19-9. Thirty-eight patients with
pancreatic cancer were enrolled in the
Volume 41, Number 2, March 2012
study. Patients’ characteristics are summarized in Table 1. We prospectively collected 86 serum samples for determination
of CA 19-9 levels and 86 plasma samples
for analysis of K-ras mutations of these
patients as described previously5Y7 at the
time when contrast-enhanced CT with thin
(1 mm) sections of the abdomen was performed during the clinical follow-up after
initial presentation.
Plasma K-ras mutations were identified in 15 (39%) of 38 patients with
pancreatic cancer, which is in agreement
with previous studies.3,8 Elevated CA 199 levels were found in 29 (76%) of the
38 patients using a cutoff value higher
than 37 IU/mL. Levels of CA 19-9 were
elevated in 62 serum samples (72%), in
which the K-ras assay in corresponding
plasma samples showed a mutation in 13
cases (21%). Furthermore, in 3 (13%) of
24 plasma samples with corresponding
CA 19-9 levels lower than 37 IU/mL, the
TABLE 1. Patients’ Characteristics
Characteristics
Sex
Male
Female
Ratio, male/female
Age, yrs
Median
Range
Survival, mo
Median
Range
Tumor location
Head of pancreas
Body of pancreas
Tale of pancreas
Resectability
Resectable
Unresectable
Clinical stage
T1
T2
T3
T4
CA 19-9, IU/mL
G37
Q37
K-ras Gene expression
Wild-type K-ras
K-ras mutation
No. Patients
21
17
1.24 : 1
61.9
35.6Y81.9
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18
2Y53
29
5
4
17
21
1
5
12
20
9
29
23
15
323
Letters to the Editor
result of the assay was positive for K-ras
mutation.
Computed tomographic findings of
complete remission, partial remission, and
stable disease were associated with plasma
K-ras wild type in 91% (10/11), 80% (4/5),
and 89% (17/19) of the cases, respectively.
CA 19-9 serum levels were elevated in
50% (7/14) serum samples, whereas corresponding CT scans showed disease remission and plasma samples showed
no K-ras mutation. Otherwise, CA 19-9
serum levels were normal in all patients
with detectable K-ras mutation, whereas
the corresponding CT scan showed disease remission. Computed tomographic
findings of disease progress were associated with plasma K-ras mutations in 24%
(12/51) of the cases. Of the remaining
39 plasma samples with K-ras wild-type
verification, despite signs of disease progress in CT, 32 (82%) corresponding serum
samples showed elevated CA 19-9 levels.
Detectable K-ras mutations in the plasma
were clearly associated with corresponding CT scans with signs of progressive
disease in 75% (12/16), whereas at the
time of verification of plasma K-ras wild
type, 44% (31/70) of corresponding CT
scans showed no signs of disease progression or stable disease (Fig. 1). The association was even more evident when
combining results of CT scans and K-ras
analysis with corresponding serum levels
of conventional tumor marker CA 19-9:
K-ras mutations and elevated CA 19-9
were associated with CT findings of progressive disease in all but one case (12/13),
Pancreas
whereas K-ras wild-type and normal CA
19-9 serum levels were associated with CT
signs of disease remission or stable disease
in most of the cases (14/21). Otherwise,
of 70 plasma samples with detection of Kras wild type, 39 (56%) were associated
with CT signs of progressive disease; but
when additionally considering normal CA
19-9 levels, only 7 (10%) plasma samples
with K-ras wild type were associated with
corresponding disease progress in CT.
Likewise, of 16 plasma samples with detection of K-ras mutation, 2 (13%) were
associated with CT signs of disease remission; but when elevated CA 19-9 levels
were considered in addition, then all plasma samples with detectable K-ras mutations
were associated with corresponding disease progress in CT.
Taken together, our results suggest
that detection of K-ras mutation in the
plasma of patients with pancreatic cancer
is a reliable marker of the course of disease, as CT findings of regressive or stable
disease were associated with plasma K-ras
wild type in most of the cases, and detectable K-ras mutations in the plasma
were clearly associated with corresponding CT scans with signs of progressive
disease. Although CT findings of disease
progress were not necessarily associated
with plasma K-ras mutations, combined
determination of K-ras mutation and conventional tumor marker CA 19-9 led to
a highly conclusive correlation with CT
findings. In addition, K-ras analysis is
suitable to add valuable information to
serial monitoring of CA 19-9 levels, as we
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Volume 41, Number 2, March 2012
observed misleadingly elevated CA 19-9
levels in serum samples, whereas corresponding CT scans showed disease remission and plasma samples showed no
K-ras mutation. Furthermore, some 5% to
10% of the population do not express
Lewis antigens and do not have detectable
CA 19-9 levels, and CA 19-9 is elevated in
only approximately 65% of individuals
with a resectable pancreatic cancer.9 Thus,
the combination of both tests, that is, the
detection of K-ras alterations in the DNA
of peripheral blood and the determination of CA 19-9 level, could be useful to
assess cancer diagnosis in patients with
normal or noncontributive CA 19-9 levels
and also to provide additional supportive
information.
In conclusion, we provide further
evidence that detection of K-ras mutations in circulating tumor DNA may serve
as a biomarker for disease progression
and could therefore be useful for detection
and prognostic evaluation of pancreatic
carcinoma. Our approach of noninvasive,
convenient, and extremely highly sensitive
K-ras mutation analysis in plasma might
provide diagnostic and prognostic information to physicians. However, the diagnostic finding of K-ras mutations has to be
tempered by complementary imaging studies, laboratory tests (eg, CA 19-9) and the
particular clinical context.
The authors declare no conflict of
interest.
FIGURE 1. Correlation of Kirsten rat sarcoma (K-ras) gene expression analysis in plasma (Wt, wild type; Mut, mutation) and serum levels of
tumor marker carbohydrate antigen (CA) 19-9 (in IU/mL) with findings of contrast-enhanced CT of the abdomen during the clinical
follow-up setting in patients with pancreatic cancer.
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Pancreas
&
Volume 41, Number 2, March 2012
Jan Däbritz, MD
Department of Medical
Oncology and Hematology
Charité School of Medicine
Campus Virchow-Klinikum, Germany
Department of General Pediatrics
University Children’s Hospital Muenster
Münster, Germany
[email protected]
8. Uemura T, Hibi K, Kaneko T. Detection of
k-ras mutations in plasma DNA of pancreatic
cancer patients. J Gastroenterol.
2004;39:56Y60.
9. Goggins M. Identifying molecular markers
for the early detection of pancreatic
neoplasia. Semin Oncol. 2007;34(4):
303Y310.
Roman Preston, MD
Department of Medical
Oncology and Hematology
Charité School of Medicine
Campus Virchow-Klinikum, Germany
Department of Nephrology and
General Medicine
University Hospital of Cologne
Cologne, Germany
Joachim Hänfler, PhD
Helmut Oettle, MD, PhD
Department of Medical
Oncology and Hematology
Charité School of Medicine
Campus Virchow-Klinikum, Germany
Letters to the Editor
Total Gastric Necrosis
Subsequent to Acute
Pancreatitis
To the Editor:
cute pancreatitis accompanied by vascular complications is potentially lethal. Most commonly, patients develop
thrombosis of parapancreatic veins, or they
bleed into pseudocysts. Furthermore, they
may show erosions or arterial pseudoaneurysms of upper gastrointestinal vessels.
Total gastric necrosis as a complication of acute pancreatitis is very uncommon because the stomach has a robust
blood supply, which includes side branches
A
of the celiac trunk and the upper mesenteric artery.
The causes of gastric necrosis can
be vascular, toxic, inflammatory, mechanical, infectious, autoimmune, or idiopathic
(Table 1).
Recently, we treated a 50-year-old
patient with total gastric necrosis as a complication of an alcohol-induced acute pancreatitis who underwent a gastrectomy with
Roux-en-Y procedure, left pancreatic resection, splenectomy, and cholecystectomy.
The patient was admitted to the hospital because of severe upper abdominal
pain and vomiting. He had a history of
alcohol abuse and denied any history of
abdominal surgery or trauma. A few days
earlier, he had drunk more alcohol than
usual. No other concomitant diseases were
known.
Laboratory investigations revealed a
leukocytosis of 15.6 103/mm3 and a
platelet count of 118 10$9/L. Electrolytes
were within the reference range. Liver enzymes: aspartate transaminase, 155 U/L;
alanine transaminase, 79 U/L; Gamma
REFERENCES
1. Wu X, Lu XH, Xu T. Evaluation of the
diagnostic value of serum tumor markers,
and fecal k-ras and p53 gene mutations
for pancreatic cancer. Clin J Dig Dis.
2006;7:170Y174.
2. Chen H, Tu H, Meng ZQ, et al. K-ras
mutational status predicts poor prognosis
in unresectable pancreatic cancer. Eur J
Surg Oncol. 2010;36(7):657Y662.
3. Olsen CC, Schefter TE, Chen H, et al. Results
of a phase I trial of 12 patients with locally
advanced pancreatic carcinoma combining
gefitinib, paclitaxel, and 3-dimensional
conformal radiation: report of toxicity
and evaluation of circulating K-ras as a
potential biomarker of response to therapy.
Am J Clin Oncol. 2009;32(2):
115Y121.
4. Castells A, Puig P, Móra J, et al. K-ras
mutations in DNA extracted from the plasma
of patients with pancreatic carcinoma:
diagnostic utility and prognostic significance.
J Clin Oncol. 1999;17(2):578Y584.
5. Däbritz J, Preston R, Hänfler J, et al.
Follow-up study of K-ras mutations in the
plasma of patients with pancreatic cancer:
correlation with clinical features and
carbohydrate antigen 19-9. Pancreas.
2009;38(5):534Y541.
6. Preston R, Däbritz J, Hänfler J, et al.
Mutational analysis of K-ras codon 12 in
blood samples of patients with acute
myeloid leukemia. Leuk Res. 2010;34(7):
883Y891.
7. Däbritz J, Hänfler J, Preston R, et al.
Detection of Ki-ras mutations in tissue and
plasma samples of patients with pancreatic
cancer using PNA-mediated PCR clamping
and hybridisation probes. Br J Cancer.
2005;92(2):405Y412.
* 2012 Lippincott Williams & Wilkins
TABLE 1. Etiology of Total and Near-Total Gastric Necrosis
Cases
Vascular
Toxic/Caustic
Mechanical
Inflammatory
Infectious
Autoimmune
Idiopathic
3
1
1
2
1
1
3
1
1
5
1
1
2
1
1
1
1
1
1
1
1
1
1
2
2
2
1
Cause
Study/Case Report
Celiac artery thrombosis
Celiac artery thrombosis
Aberrant arterial anatomy
Cholesterol embolisms
Celiac artery thrombosis
Caustic ingestion
Caustic ingestion
Battery acid ingestion
Caustic ingestion
Caustic ingestion
Massive gastric dilatation
Anorexia/bulimiaVmassive
gastric dilatation
Gastroaxial volvulus
Massive dilatation
Incarceration in hiatal hernia
Incarceration in hiatal hernia
Dilatation due to heavy meal
Dilatation due to heavy meal
Acute pancreatitis
Acute pancreatitis
Emphysematous gastritis
Acute necrotizing gastritis
Antiphospholipid
syndrome/vascular occlusion
Primary antiphospholipid syndrome
Cohen,1 1951
Kumaran et al,2 2006
Challand et al,3 2008
Bong et al,4 2007
Scheppach et al,5 1993
Lin et al,6 1991
Davis,7 1972
Casetti et al,8 1980
Franke et al,9 2008
Ismael et al,10 1996
Zivkovic et al,11 1984
Lunca et al,12 2005
Abdu et al,13 1987
Bortul et al,14 2004
Wilson et al,15 1992
Kosinski et al,16 1992
Lortat-Jacob et al, 17 1967
Trindade et al,18 2008
Turan et al,19 2003
Scholefield,20 1988
Hsu et al,21 2009
Agarwal et al,22 2009
Dharap et al,23 2003
Srivastava et al,24 2010
Sánchez-Guerrero,25 1992
McKelvie et al,26 1994
Vargas et al,27 2001
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