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Ihor I. Izhnin

Olena I. Fitsych

Anton A. Pishchagin

Andrei P. Kokhanenko

Alexander V. Voitsekhovskii

Stanislav M. Dzyadukh

Alexander I. Nikiforov

NANO EXPRESS Open Access
Temperature spectra of conductance of Ge/
Si p-i-n structures with Ge quantum dots
Ihor I. Izhnin1*, Olena I. Fitsych1, Anton A. Pishchagin2, Andrei P. Kokhanenko2, Alexander V. Voitsekhovskii2,
Stanislav M. Dzyadukh2 and Alexander I. Nikiforov2,3
Abstract
This work presents results of investigation of Ge/Si p-i-n structures with Ge quantum dots in the i-region by the
method of admittance spectroscopy. The structures contain multiple layers with Ge quantum dots separated by
thin 5 nm layers of Si in the intrinsic region. Two peaks are observed on the temperature dependences of
conductance of the investigated heterostructures. It is revealed that the second peak is broadened and corresponds
to a system of closely lying energy levels.
Keywords: GeSi, Molecular-beam epitaxy, Quantum dot, Admittance spectroscopy, Energy levels of spatial
quantization
PACS: 73.21.La, 73.40.Lq, 73.63.Kv
Background
In the last few years, creating semiconductor structures
with new physical properties has been the primary goal
of nanotechnology, which has the aim of expanding the
limits of applicability of semiconductor materials. The
discovery of new physical properties allows for creating
new devices using advanced technology of silicon micro-
electronics [1–4]. Also, in recent years, the interest in
photoelectric properties of Ge/Si heterostructures (pri-
marily designed for the spectral range of 1.3–1.55 μm)
has increased. New types of photodetectors based on
silicon-germanium low-dimensional heterostructures
using intrasubband and intersubband transitions are in-
tensively being developed. Such devices may be used in
optoelectronic communication systems and remote
monitoring [2, 5]. Large attention to Ge/Si structures is
caused due to the possibility of their use in solar energy.
Ge/Si heterostructures with Ge quantum dots have
turned out to be promising for creating high-efficiency
solar cells. Theoretical estimations predict efficiency of
53% for solar cells based on Si with Ge quantum dots
[6]. Improving the efficiency of devices based on Ge/Si
heterostructures with Ge quantum dots is possible due
to the effects of spatial quantization.
Nowadays, admittance spectroscopy is extensively used
to obtain the information about some properties of
semiconductor heterostructures with quantum dots. A
large number of studies have been devoted to investigat-
ing structures containing Schottky barriers by the
methods of admittance spectroscopy [7–9]. But it should
be noted that studies of the characteristics of p-i-n
structures based on Ge/Si material system by the
method of admittance spectroscopy are still extremely
rare. However, for device applications such as solar cells
and photodetectors, p-i-n-structures are very important.
In this work, we show the possibility of studying p-i-n-
structures based on Si with Ge quantum dots by admit-
tance methods.
Methods
In this paper, we present the experimental results on
synthesis of Si/Ge p-i-n structures with Ge quantum
dots in the i-region and their investigation by the
method of admittance spectroscopy.
The samples were fabricated by molecular beam epi-
taxy in an ultra-high vacuum installation “Katun-C” in
the Institute of Semiconductor Physics. Evaporation of
silicon and germanium was carried out by electron beam
* Correspondence: i.izhnin@carat.electron.ua
1Scientific Research Company “Carat”, Stryjska St. 202, Lviv 79031, Ukraine
Full list of author information is available at the end of the article
© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.
Izhnin et al. Nanoscale Research Letters  (2017) 12:131 
DOI 10.1186/s11671-017-1916-0
evaporators, and the dopants (Sb and B) were evapo-
rated from effusion cells. The analytical part of the
epitaxy chamber consists of a quadrupole mass spec-
trometer, a quartz thickness gauge, and a reflection high
energy electron diffractometer. The growth of Ge
quantum dots was carried out on Si(100) substrates with
misorientation less than 0.5° at 500 °C. The growth rates
of Ge and Si layers were 0.025 and 0.113 nm/s,
respectively.
For investigations, samples of photoelements with
different size and topology of the active region were pre-
pared. Heavily doped p- and n-regions were obtained by
doping with B and Sb, respectively. The remaining re-
gions including quantum dots were not intentionally
doped and served as i-layers. Ohmic contacts to the p-
and n-regions were fabricated by evaporation of Al
layers followed by thermal annealing at 450 °C.
We have studied 3 types of samples. All of them are p-
i-n structures, but type 1 samples are p-i-n structures
without layers of quantum dots, while type 2 and type 3
samples contain multiple layers of Ge quantum dots in
the intrinsic region. The height of Ge hut-clusters is
1.5–3 nm, lateral size is 10–40 nm, and surface density
is ~1011 cm−2. The intrinsic region of type 2 samples
contains 30 layers of 6 monolayer Ge quantum dots sep-
arated by 5 nm silicon layers. The intrinsic region of
type 3 samples is similar to that of type 2, but every 10
layers of Ge quantum dots are additionally separated by
100 nm of Si.
Measurements were performed on an automated ad-
mittance spectroscopy installation [10]. During one cycle
of temperature scanning, measurements of the frequency
and temperature dependences of capacitance and
conductance, as well as of current-voltage characteristics
of the studied structures were carried out in the
temperature range 10–300 K.
Results and discussion
By analogy with deep levels in semiconductors, the
principle of admittance spectroscopy of structures with
quantum dots is based on measuring the complex con-
ductivity of the system: it changes when discrete energy
levels recharge due to emission of charge carriers and
their capture by localized states. The temperature spec-
tra of conductance (G-T) at different frequencies of the
test signal and different bias voltages are often consid-
ered to be the most informative.
In the temperature dependence of conductance of type
1 samples, a maximum was observed at low tempera-
tures (25–40 K). The observed maximum of conduct-
ance corresponds to a discrete energy level. The position
of this peak shifts on the temperature scale as the
frequency of the applied signal changes (Fig. 1).
Conductance peak position for these samples remains
constant with changes in the applied bias voltage.
Similar results were obtained in studies of type 2 and
type 3 samples. Figures 2 and 3 show the temperature
conductance spectra of type 2 and type 3 samples mea-
sured at different voltages and different frequencies.
The charge carrier emission rate from a discrete level
is determined by the expression (1):
e ¼ AT2 exp − Ea
kT
 
; ð1Þ
where T is the temperature, k is the Boltzmann’s
constant, Ea is the activation energy, A is the pre-
G
/ω
, p
F
0
200
400
600
800
1 000
1 200
1 400
1 600
T, K
20 25 30 35 40 45 50
2
3
4
1
Fig. 1 Temperature spectra of conductance for sample type 1
measured at the applied bias voltage of –0.5 V and various
frequencies of the test signal 1 2000 kHz, 2 1500 kHz, 3 1000 kHz,
and 4 500 kHz. The inset shows the structure of samples
G
/ω
, p
F
0
1 000
2 000
3 000
4 000
5 000
6 000
7 000
8 000
T, K
20 25 30 35 40 45 50 55
1
2
3
4
Fig. 2 Temperature spectra of conductance for sample type 2
measured at the applied bias voltage of –0.5 V and various
frequencies of the test signal 1 100 kHz, 2 50 kHz, 3 10 kHz, and 4
5 kHz. The inset shows the structure of samples
Izhnin et al. Nanoscale Research Letters  (2017) 12:131 Page 2 of 5
exponential factor which does not depend on the
temperature and is proportional to the capture cross
section of the charge carriers at the localized state. The
contribution of the discrete energy levels to the conduct-
ance is determined by the following expression [10]:
GTe eωe2 þ ω2 12Vb
 1
2
; ð2Þ
where ω is the angular frequency of the test signal and
Vb is the applied voltage.
The main characteristic of a discrete energy level is
the charge carrier activation energy. To determine the
activation energy, the experimental points are plotted in
coordinates ln e = f(1/T), called an Arrhenius plot. In the
Arrhenius coordinates, dependence (1) is a straight line.
The GT/ω value has a maximum at ω = e. By plotting
maxima Tmax in coordinates ω = f(1/T), we determine
the activation energy characterizing the position of the
energy levels. We have plotted point with coordinates
ln(e/T2), 1/Tmax for each frequency, and have built the
approximating straight line. Then, we have calculated ac-
tivation energy from the slope of the line. Figure 4 shows
the Arrhenius plot for temperature spectra of conduct-
ance of type 1 samples.
In a further study of type 3 samples, a conductance
peak at low positive bias was also detected (peak 2 at
Fig. 5). This maximum is observed only at positive biases
at higher temperatures and is most pronounced at low
frequencies, while the first maximum is also observed at
negative biases.
Processing temperature spectra leads to a typical
family of Arrhenius plots suitable for finding activation
energies of the emission process. For all samples,
activation energies were calculated. For the first peak of
conductance calculated activation energies of type 1,
type 2 and type 3 samples do not depend on the applied
bias voltage and are equal to 38 ± 5, 42 ± 4, and 46 ±
4 meV, respectively. For the second peak, the calculated
activation energy at the bias voltage of 1 V is 65 ±
10 meV; at the bias voltage of 2 V, it is 165 ± 30 meV.
Figure 6 shows the band structure and energy levels of
Ge quantum dots in Si.
We observed first peak at low temperatures (~20–
40 K) for all bias voltages. From the presented figures, it
is seen that the position of this maximum in the
temperature dependence of conductance and corre-
sponding activation energies do not show a pronounced
G
/ω
, p
F
0
20
40
60
80
100
120
140
T, K
15 20 25 30 35 40 45 50
2
3
4
1
Fig. 3 Temperature spectra of conductance for sample type 3
measured at the applied bias voltage of –0.5 V and various
frequencies of the test signal 1 1000 kHz, 2 500 kHz, 3 100 kHz,
and 4 10 kHz. The inset shows the structure of samples
eT
-2
,s
-1
K
-2
1 000
1e+04
1e+05
1e+06
1e+07
1000/T, 1/K
25 30 35 40 45
12
3
Fig. 4 Arrhenius plots built for the positions of the maxima of the
temperature spectra of conductance of type 1 samples at various
bias voltages 1 −1 V, 2 −0.5 V, and 3 −0 V
G
/ω
, p
F
100
1000
1e+04
T, K
15 20 25 30 35 40 45 50 55 60 65 70 75
1
2
3
4
5
6
7
1st peak
2nd peak
Fig. 5 Temperature spectra of conductance of type 3 sample,
measured at the voltages of +1 V (1–3) and +2 V (4–6) at various
frequencies 1 1 kHz, 2 2 kHz, 3 3 kHz, 4 1 kHz, 5 2 kHz, 6 3 kHz. 7
Temperature spectra of conductance of type 1 sample, measured at
the applied bias voltage of +2 V and frequency of the test signal
of 500 kHz
Izhnin et al. Nanoscale Research Letters  (2017) 12:131 Page 3 of 5
dependence on the applied bias voltage. Recharging of
the level occurs with fixed bias voltage Vb. The charge
carrier emission rate from this level decreases at
lower temperatures, so with a decrease in the fre-
quency of the test signal, the condition of maximum
conductance is achieved at lower temperatures and at
different frequencies.
We assume that the first peak may be associated with
the impurity level in Si.
Yakimov et al. [7] conducted research on Si Schottky
barrier structure with several layers of Ge quantum dots
by admittance spectroscopy method at low tempera-
tures. They revealed the presence of two maxima in the
temperature dependence of conductance. The first max-
imum did not depend on the applied bias and corre-
sponded to a doping level.
We received another evidence of this from the com-
pared temperature spectra for type 2 and type 3 samples
with temperature spectra for type 1 samples without Ge
quantum dots. The temperature spectra for type 1 sam-
ples have the maximum at the same temperatures. So,
the discrete energy level with activation energy of ~35–
50 meV, corresponding to the first peak of the
temperature dependence of conductance, is not related
to the spatial quantization in quantum dots.
The second peak can be explained by the presence of
spatial quantization levels in the system associated with
Ge quantum dots. This peak is broadened and probably
corresponds not to a single discrete but to a system of
closely lying levels, due to the inhomogeneity of such
parameters of quantum dots as their lateral size, height,
shape, and density in the array. We explain the appear-
ance and modification of peaks by the following fact.
With a change in the applied voltage, the electrochem-
ical potential occasionally crosses the discrete energy
levels and it produces oscillations in the charge density
distribution. The reason for this is the thermionic
emission of charge carriers from a discrete level.
Discrete level gives partial charge density increment.
This increment of charge leads to an increase in the ex-
ternal circuit current measured as a change in conduct-
ance of a sample.
Thus, analysis of the results and literature data allows
for making the following assumptions. The lack of size
quantization effect in type 2 structure (absence of the
second peak in the temperature dependence of conduct-
ivity) may be due to the accumulation of strains during
the growth of successive Ge layers, which leads to an in-
crease in the size of the quantum dots [11], and/or non-
uniform strain relaxation, resulting in a large number of
defects [12]. Introduction of thick Si spacer layers in
type 3 structure should significantly reduce these factors,
which leads to the appearance of the size quantization in
Ge quantum dots and, thus, the appearance of the
second peak in the temperature dependence of
conductivity.
Conclusions
This paper shows the possibility of studying Si p-i-n-
structures with Ge quantum dots by the method of ad-
mittance spectroscopy. We have investigated a number
of Si p-i-n-structure samples with different type of i-
layers. Only for sample containing 30 layers of 6 mono-
layer Ge quantum dots separated by 5 nm silicon layers
in which every 10 layers of Ge quantum dots were add-
itionally separated by 100 nm of Si (type 3) was observed
two peaks on the temperature dependences of conduct-
ance. The first peak was observed at any bias voltage, al-
though the second peak was observed in the narrow
voltage range. Position of the first peak does not depend
on the applied bias voltage, the second peak shifts on
temperature scale with changing the bias voltage from 1
to 2 V. We have calculated activation energies for both
peaks. The first peak of the temperature dependence of
Fig. 6 Schematic image of the band structure and energy levels of Ge quantum dots in Si
Izhnin et al. Nanoscale Research Letters  (2017) 12:131 Page 4 of 5
conductance may be associated with the impurity level
in Si (46 meV). The second peak can be explained by
the presence of spatial quantization levels in the system
associated with Ge quantum dots 65 and 165 meV. Ap-
plying thick Si spacers in type 3 structure allows for
eliminating the strain and for obtaining the highest de-
gree of uniformity of the array of quantum dots with the
minimum number of defective islands, which determines
the appearance of the size quantization in the Ge
quantum dots.
Acknowledgements
There are no acknowledgements.
Authors’ contributions
AVV conceived the idea of the study. AIN and APK fabricated the Ge/Si
heterostructures with Ge quantum dots by molecular beam epitaxy. SMD
and AAP carried out the electrical measurement of Ge/Si heterostructures.
AVV, III, OIF, SMD, AAP, and APK interpreted the experiments. III and AAP
wrote the manuscript. All authors read and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Author details
1Scientific Research Company “Carat”, Stryjska St. 202, Lviv 79031, Ukraine.
2National Research Tomsk State University, Lenina Av. 36, Tomsk,
Russia634050. 3A.V. Rzhanov Institute of Semiconductor Physics SB RAS,
Akademika Lavrent`eva Av. 13, Novosibirsk, Russia630090.
Received: 20 December 2016 Accepted: 13 February 2017
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SHORT COMMUNICATION
Dilemmas in the management of screen-detected lesions
in patients at high risk for pancreatic cancer
Isaura S. Ibrahim1 • Bert A. Bonsing2 • Rutger-Jan Swijnenburg2 •
Lieke Welling2 • Roeland A. Veenendaal1 • Martin N. J. M. Wasser3 •
Hans Morreau4 • Akin Inderson1 • Hans F. A. Vasen1
Published online: 12 July 2016
 The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract In 3–5 % of all cases of pancreatic ductal ade-
nocarcinoma (PDAC), hereditary factors influence etiol-
ogy. While surveillance of high-risk individuals may
improve the prognosis, this study describes two very dif-
ferent outcomes in patients with screen-detected lesions. In
2000, a surveillance program of carriers of a CDKN2A/
p16-Leiden-mutation consisting of annual MRI was initi-
ated. Patients with a suspected pancreatic lesion undergo
CT-scan and Endoscopic Ultrasound, and surgery is
offered when a lesion is confirmed. In 2015, two patients
with a screen-detected solid lesion were identified. In both
patients, lesions were visible on MRI and CT scan, while
the EUS was unremarkable. Surgical resection of the head
of the pancreas resulted in nearly fatal complications in the
first patient. This patient was shown to have a benign
lesion. In contrast, timely identification of an early cancer
in the second patient was accompanied by an uneventful
postoperative course. These cases underline the risks
inherent to a PDAC prevention program. All patients
should be fully informed about the possible outcomes
before joining a surveillance program.
Keywords Pancreatic ductal adenocarcinoma  PDAC 
Genetic predisposition  CDKN2A mutation  p16-Leiden
mutation  Surveillance  Pylorus-preserving
pancreaticoduodenectomy  Complications
Introduction
Pancreatic ductal adenocarcinoma (PDAC) is considered
one of the most aggressive forms of cancer. With PDAC
currently ranking fourth in terms of cancer-related deaths
in the United States [1], the prognosis will only improve if
the tumour can be detected and treated at an earlier stage.
Approximately 3–5 % of all patients with PDAC have a
genetic predisposition that results in an increased risk of
developing the tumor [2] and a substantial proportion of
these patients carry an underlying gene defect in CDKN2A/
p16-Leiden (Familial Atypical Multiple Mole Melanoma,
FAMMM syndrome), STK11 (Peutz-Jeghers syndrome),
the BRCA1/2 genes (Hereditary breast cancer) or one of the
MMR genes (Lynch syndrome) [3].
Because surveillance might improve the prognosis in
asymptomatic, high-risk individuals, in 2000 a surveillance
program for CDKN2A/p16-Leiden mutation carriers was
initiated at the department of Gastroenterology and Radi-
ology at the Leiden University Medical Centre (LUMC).
Surveillance consists of a yearly MRI, with an option for
EUS between two MRI scans. In cases where a pancreatic
lesion is suspected, an EUS and CT scan is performed in
order to confirm the presence of the lesion. If the lesion is
confirmed, pancreatic surgery is offered.
In this report, we describe surveillance and treatment
results for two CDKN2A/p16-Leiden patients with a screen-
detected lesion.
& Hans F. A. Vasen
hfavasen@stoet.nl
1 Department of Gastroenterology and Hepatology, Leiden
University Medical Centre, Albinusdreef 2, 2333 ZA Leiden,
The Netherlands
2 Department of Surgery, Leiden University Medical Centre,
Leiden, The Netherlands
3 Department of Radiology, Leiden University Medical Centre,
Leiden, The Netherlands
4 Department of Pathology, Leiden University Medical Centre,
Leiden, The Netherlands
123
Familial Cancer (2017) 16:111–115
DOI 10.1007/s10689-016-9915-3
Case 1
The first patient, a 55-year-old male with a CDKN2A/p16-
Leiden mutation, was referred to the Department of Gas-
troenterology and Hepatology at the Leiden University
Medical Centre in 2011 to discuss the option of pancreatic
surveillance. The patient had no known family history of
PDAC, and quit smoking in 2003.
The advantages and disadvantages of the surveillance
program were discussed with the patient before he gave
informed consent. In the summer of 2015, a solid 8 mm
lesion in the uncinate process of the pancreas was
detected by MRI (Fig. 1, upper panel). Retrospectively, a
small lesion was already visible on the previous MRI in
2014. The patient did not report any complaints and all
blood tests were normal, including CA19.9. Subsequent
CT scanning confirmed the presence of a solid 10 mm
lesion (Fig. 1, lower panel), whereas EUS was normal.
The patient was discussed by a multidisciplinary team
and resection was recommended because two of the three
imaging tools showed the presence of a solid lesion.
During surgical exploration, a small lesion was palpated
in the uncinate process of the pancreas and a pylorus-pre-
serving pancreaticoduodenectomy (PPPD) was performed.
Pathological examination of the surgical specimen showed
a 3 mm small area with sclerotic stroma and inflammation.
Amidst the sclerosis ductular proliferation, with focal
cribriform architecture was found. SMAD4 and p53
immunostaining was normal. Taking everything into
account it was concluded that there was no evidence of
(pre)cancer. A total of 23 lymph nodes were identified, all
of which were free of tumor.
One day after surgery the patient developed symptoms
suggesting leakage of the choledochojenunostomy. During re-
exploration the anastomosis was revised. Eight days after the
initial surgery, leakage of the pancreatico-jejunostomy led to a
re-laparotomy, with revision of the anastomosis with surgical
drains left in situ. Nine days after this intervention, the
patient’s condition deteriorated. Evidence for a new leakage
of the pancreatic anastomosis led to a completion pancreate-
ctomy. Eighteen weeks later, a retroperitoneal debridement of
necrosis in the former pancreatic bed was performed. Finally,
the patient developed a thoracic empyema and a subphrenic
abscess treated by thoracotomy and decortication. Following
the last intervention the patient recovered slowly and he was
discharged in a relatively good physical condition, 5 months
after the initial surgery. His diabetes is currently managed with
four daily doses of insulin.
Fig. 1 MRI (upper panel) and CT-scan (lower panel) of the pancreas in case 1
112 I. S. Ibrahim et al.
123
Case 2
The second patient, a 50-year-old male with a CDKN2A/
p16-Leiden mutation, was referred to the department of
Gastroenterology and Hepatology. He underwent treatment
for melanoma at the ages of 36 and 40. He was asymp-
tomatic and he had never smoked. His father died of PDAC
at age 52. After discussion on the benefits and drawbacks,
the patient decided to participate in the surveillance pro-
gram (2012). An MRI scan in November 2015 showed a
possible 17 mm lesion with oedema in the head of the
pancreas (Fig. 2, upper panel). Retrospectively, a smaller
oedematous area was present at this site on the previous
MRI scan. CT scanning confirmed the presence of a solid
10 mm lesion in the same area (Fig. 2, lower panel), while
the EUS was unremarkable. Blood tests did not show any
abnormalities. The findings were discussed by the Leiden
multidisciplinary team and a PPPD was offered. Following
surgery, pathological examination of the surgical specimen
showed a 9 mm moderately differentiated PDAC, sur-
rounded by inflammation. The resection margins were free
(closed margin 0.3 mm facing the SMV) although there
was growth into the peripancreatic tissue. All 15 detected
lymph nodes were free of cancer. The patient recovered
well after surgery and did not encounter any complications.
He was discharged from hospital, in good physical condi-
tion, 8 days after initial surgery.
Discussion
These two cases clearly illustrate the dilemmas faced in the
surveillance of individuals at high-risk for PDAC. The first
patient experienced nearly fatal complications due to sur-
gery and was found to have a benign lesion. This is an
example of a worst-case scenario that may occur in this
type of surveillance program. The second patient, diag-
nosed shortly after the first case, had very similar imaging
findings, an uneventful course after surgery, and was
eventually shown to have an early cancer.
Several questions arise regarding these two patients:
(a) Did the findings, especially in the first patient, justify
surgery? (b) Could the benign nature of the lesion in the
first patient have been predicted? (c) How can the
surveillance programs be improved? (d) How can a dev-
astating course, as seen in the first patient, be prevented?
Regarding the first question, the two imaging techniques
(MRI and EUS) reportedly show a high sensitivity and
specificity [4], with MRI usually regarded as the best tool
to identify cystic lesions and EUS as the best technique for
the identification of solid lesions [5]. In both cases reported
here the presence of a solid lesion was shown on MRI and
CT, whereas the EUS was unremarkable. The fact that the
lesion was palpated in both patients during surgical
exploration confirmed the imaging findings and justified
surgery in view of the high risk of PDAC. Lesion growth is
a strong indicator for malignancy, but both patients showed
only slight lesional growth. Due to the rapid growth of
PDAC, another argument in favour of surgery is the short
window of time between the detection of a lesion and
development of metastatic disease [6].
In relation to the second issue, prediction of the benign
nature of a lesion, differentiation of benign and malignant
lesions by FNA biopsy might have been considered. In this
particular case no abnormalities were found on EUS, ruling
out EUS-guided biopsy. In retrospect, even if the lesion
had been visible on EUS, performance of an FNA biopsy
would not have been useful in decision-making in this case
because a negative FNA result does not exclude the pres-
ence of PDAC.
The second patient was diagnosed shortly after dis-
charge of the first patient. In view of the devastating course
in the first patient combined with the identification of a
benign lesion, we were very hesitant to offer surgery again.
However, based on the same arguments and after consul-
tation with international experts, surgery was offered. The
pathological findings following surgery in this case sub-
sequently confirmed that this was the right decision and
suggested that postponement of surgery would have
impaired the patient’s outcome.
Regarding the third question—improvement of surveil-
lance methods—this case report underlines the urgent need
for modification of screening methods, especially regarding
improvements in the sensitivity of MRI imaging of the
pancreas. Additional screening tools should also be
developed. At present, the value of the FDG-PET scan in
the detection of PDAC is questionable, because the mini-
mum size of lesions detectable by this technique is about
10 mm. However, developments in PET tracers that target
specific tumor biomarkers that occur as a consequence of
the CDKN2A/p16-Leiden defect could potentially lead to
earlier detection [7].
Another way to improve the surveillance program is the
use of circulating tumour markers. Slater et al. [8, 9]
reported promising results on the use of tumour markers,
including micro-RNAs 196a and b, LCN2, and TIMP1. In a
small pilot study, the application of proteomics allowed us
to differentiate between malignant and benign lesions [10].
However, these findings should be confirmed in larger
studies.
The final question concerns how the risks of serious
complications due to surgery can be minimized. Recent
studies suggest that mortality rates for pancreaticoduo-
denectomies procedure lie somewhere between 0.5 and
6 %, with a morbidity rate of up to 40 % [11, 12]. A recent
Dilemmas in the management of screen-detected lesions in patients at high risk for pancreatic… 113
123
decision model study showed that the possible benefits of a
surveillance program may be lost if the mortality rate is
slightly increased [13].
The only way to achieve the lowest possible mortality
and morbidity rates is to restrict prevention programs to
expert centres that carry out larges volume of pancreatic
surgeries. Moreover, it is very important to discuss the
advantages and disadvantages with a patient prior to their
participation in a surveillance program so that the patient is
fully aware of the risks. Advantages of the program
in CDKN2A/p16-Leiden mutation carriers are that more
tumours are identified at a resectable stage (75 % vs.
15–20 % in symptomatic patients) and that the prognosis
of patients with screen-detected tumours is better (5-year
survival is 24 %) than that of symptomatic patients
(5–7 %) [14].
Fig. 2 MRI (upper panel) and CT-scan (lower panel) of the pancreas in case 2
114 I. S. Ibrahim et al.
123
Disadvantages include, (1) the surveillance program
cannot guarantee that PDAC is always detected at an early
and curable stage, (2) the screening protocol is burdensome
and may cause anxiety before and shortly after the
screening procedure, (3) there may be false positive and
false negative cases, and finally, (4) treatment consists of
major surgery, a pancreaticoduodenectomy or distal pan-
createctomy depending on the site of the tumor, all of
which are associated with substantial morbidity and
mortality.
These case reports illustrate the difficult decisions that
have to be made in high-risk individuals with a suspected
lesion in the pancreas. All involved physicians, together
with the patient, should be aware of all possible outcomes
of the intervention.
Acknowledgments We would like to thank the following colleagues
who were involved in the management of these patients: Birgitta
Zomer, Femke de Snoo, Frederik Hes, Christie van Asperen, Pia de
Koning Gans and Wouter de Vos tot Nederveen Cappel. We also
thank Mimi Canto (Baltimore, US), Detlef Bartsch and Thomas Gress
(Marburg, Germany) for their help and advice.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://crea
tivecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
made.
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Dilemmas in the management of screen-detected lesions in patients at high risk for pancreatic cancer

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