DOI:10.2214/AJR.07.2758
AJR 2008; 191:387-395
© American Roentgen Ray Society
The Role of Imaging in the Diagnosis, Staging, and Management of Testicular Cancer
S. Aslam Sohaib1,
Dow-Mu Koh1 and
Janet E. Husband1
1 All authors: Department of Diagnostic Radiology, Royal Marsden Hospital, Down
Rd., Sutton, Surrey SM2 5PT, England.
Received June 20, 2007;
accepted after revision February 4, 2008.
Address correspondence to S. A. Sohaib.
CME
This article is available for CME credit. See
www.arrs.org
for more information.
Abstract
OBJECTIVE. The objective of this article is to describe recent
developments in imaging patients with testicular germ cell tumors (GCTs).
CONCLUSION. Most patients with testicular GCTs can now be expected
to be cured, so the focus on management moves toward identifying patients who
need more aggressive treatment and avoiding long-term complications. CT
remains central in the selection of a management strategy, although the roles
of MRI and PET continue to evolve.
Keywords: CT • genitourinary imaging • germ cell tumor • oncologic imaging • testicular cancer
Introduction
More than 95% of patients with testicular germ cell tumors (GCTs) can be
cured by current treatments. In recent years, attention has focused not only
on improving cure rates in patients for whom treatment has historically been
unsuccessful but also on optimizing treatment in the groups with a good
prognosis, with the aim of limiting the long-term adverse effects of
treatment.
Imaging plays a pivotal role in the management of patients with testicular
GCT: It is crucial for establishing the presence and extent of metastatic
disease and subsequently for assessing response to treatment, evaluating
suitability for surgery of residual masses, and detecting sites of relapse. CT
and chest radiography remain the main radiologic techniques used in these
settings, although MRI, PET with 18F-FDG, and sonography also have
a place in certain clinical situations. This article reviews the current role
of imaging in the management of patients with testicular GCT.
Clinical Background
Epidemiology
GCTs of the testes are the most common malignant tumor in males who are
between 15 and 44 years old, with approximately 8,000 new cases per year in
the United States [1]. The
incidence of testicular cancer has been rising and has almost doubled in the
past 40 years [2]. Risk factors
for the development of testicular GCT include a history of testicular GCT,
cryptorchidism, infertility, testicular dysgenesis, and a positive family
history [2].
Pathology
GCTs are classified as either nonseminomatous GCTs, which account for
approximately 60% of tumors, or seminomas, which account for approximately
40%. Accurate classification is important because it determines the type of
treatment. Nonseminomas are clinically more aggressive and often include
multiple cell types such as embryonal cell carcinoma, choriocarcinoma, yolk
sac tumor, and teratoma. Teratoma may be either mature or immature. If both
seminoma and elements of nonseminoma are present, management follows that for
a nonseminoma.
Serum tumor markers 
-fetoprotein, HCG, and lactate dehydrogenase
(LDH) are critical in diagnosing GCTs, determining prognosis, and assessing
treatment response. The -fetoprotein level is higher than normal in up
to 65% of patients with nonseminomatous GCT, but it is never raised in those
with pure seminomatous tumors. The HCG level is raised in up to 60% of
patients with advanced nonseminomatous GCT and in 15–20% of those with
seminoma. The LDH level is raised in most patients with advanced
nonseminomatous GCT and seminoma.
Pattern of Spread
Testicular tumors spread by the lymphatic route through channels that
accompany testicular vessels to the retroperitoneal lymph nodes. Right-sided
tumors spread to the aortocaval nodes (Figs.
1A and
1B), precaval nodes, and right
paracaval and retrocaval nodes. Left-sided tumors spread to the left
paraaortic nodes (Fig. 2) and
preaortic nodes. Lymphatic spread may also occur to nodes lateral to the
paracaval paraaortic group, the so-called echelon nodes
(Fig. 3). These nodes are an
unusual site of disease, more frequently seen at the time of relapse than at
initial staging.
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Fig. 1A —42-year-old man with stage IIA disease from right-sided
nonseminomatous germ cell tumor. Contrast-enhanced CT shows response to
chemotherapy. CT scan shows 10-mm aortocaval node (arrow) behind
third part of duodenum.
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Fig. 1B —42-year-old man with stage IIA disease from right-sided
nonseminomatous germ cell tumor. Contrast-enhanced CT shows response to
chemotherapy. CT scan obtained after patient underwent treatment with
chemotherapy shows that there has been complete response.
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Fig. 4A —21-year-old man with metastatic nonseminomatous germ cell
tumor. Contrast-enhanced CT scans show multiple lung metastases (A) and
multiple liver metastases (B), along with large retroperitoneal disease
that is invading left renal vein (arrow, B).
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Fig. 4B —21-year-old man with metastatic nonseminomatous germ cell
tumor. Contrast-enhanced CT scans show multiple lung metastases (A) and
multiple liver metastases (B), along with large retroperitoneal disease
that is invading left renal vein (arrow, B).
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Hematogenous spread in testicular cancer is predominantly to the lungs
(Figs. 4A and
4B). Other sites of metastases
in patients with advanced aggressive tumors include the brain, bone, and liver
(Figs. 4A and
4B). Brain metastases are more
common in patients with trophoblastic teratomas than any other histologic
type. Other unusual sites of disease (e.g., peritoneum, kidney, spleen) are
more frequently observed at the time of relapse in patients who have been
previously treated.
Staging Classification
Before initiating therapy, assessment of disease extent must be performed.
Guidelines from the National Comprehensive Cancer Network (NCCN) and the
European Germ Cell Cancer Consensus Group (EGCCCG) recommend that TNM staging
be used (Tables 1 and
2) and that patients are
categorized using the International Germ Cell Cancer Collaborative Group
(IGCCCG) classification, which stratifies patients into good, intermediate,
and poor prognostic groups
[3–6].
This latter classification is based on histology, location of the primary
tumor, presence of metastases, and serum marker levels
[5]
(Table 3).
Management
The management of testicular GCT depends on the pathology, staging, and
prognostic grouping of the tumor
[2,
4].
Seminoma—After orchidectomy has been performed, management
options for stage I disease, which accounts for 75% of men at diagnosis,
includes surveillance or adjuvant treatment with either radiation therapy or a
single cycle of carboplatin chemotherapy. The disease-specific survival for
stage I disease approaches 99% independent of the management strategy used.
The treatment options for stage IIA and IIB seminoma include paraaortic and
iliac node radiation therapy, chemotherapy, or a combination of chemotherapy
and radiation therapy. All three options for stage IIA and IIB provide high
rates of cure, but with differing toxicity profiles. There is general
agreement that the best treatment for stage IIC and above involves multiagent
platinum-based chemotherapy.
Nonseminomatous GCT—The options for stage I nonseminomatous
germ cell tumors after orchidectomy are surveillance or adjuvant chemotherapy
or primary retroperitoneal lymph node dissection. The standard treatment for
metastatic nonseminomatous GCT (i.e., stages II–IIIC) is multiagent
platinum-based chemotherapy, which has an overall cure rate of approximately
85%.
Diagnosis
Testicular tumors are usually diagnosed clinically and pathologically at
surgery. Imaging of the testis with sonography can help to confirm the
presence of an intratesticular mass or if there is uncertainty about the
clinical features. Testicular sonography is also helpful in assessing patients
who present with metastatic disease in whom an occult primary tumor of the
testis is suspected or examining the contralateral testis to identify the
small number of patients with bilateral synchronous tumors.
MRI has been reported to be able to distinguish between seminoma and
nonseminomatous GCT [7].
However, MRI findings are of little clinical value because appropriate
management dictates that orchidectomy be performed to obtain detailed
pathology of the tumor and is mandatory for primary treatment. MRI of the
scrotum may help if clinical and sonographic assessments cannot differentiate
an intratesticular mass from an extratesticular mass
[8].
Staging
CT remains the imaging technique of choice in staging testicular GCT. The
effective use of CT relies on good technique and a detailed knowledge of the
patterns of tumor spread, the characteristic appearances of metastatic
disease, and familiarity with potential diagnostic pitfalls.
Lymph node metastases vary in size from a single small-volume node of 1 cm
in diameter to huge intraabdominal retroperitoneal masses (Figs.
1A,
1B,
2,
4A,
4B,
5A, and
5B). Masses from seminoma are
usually of soft-tissue density (Fig.
5A) but occasionally may contain areas of relatively low density
due to central necrosis. However, large-volume masses of nonseminomatous GCT
are frequently heterogeneous in density
(Fig. 4B), being composed of
multiloculated complex cystic areas as well as soft-tissue elements.
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Fig. 5B —55-year-old man with seminoma. Contrast-enhanced CT shows
response to chemotherapy. Image obtained 6 months after A shows
excellent response with minimal soft tissue (arrow), which resolved
on subsequent imaging (not shown).
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Although the diagnosis of large-volume disease is readily made on CT, the
diagnosis of small-volume metastatic disease, thus distinguishing stage I from
stage II disease, may be extremely difficult. Such distinction is critical to
patient management because a surveillance policy may be implemented in
patients with stage I disease, whereas patients with stage II disease need
treatment, usually chemotherapy. Using a size criterion of 8 mm or larger in
the maximum short-axis diameter to define a suspicious retroperitoneal node is
associated with a high specificity but a low sensitivity
[9]. However, the results of
studies have established that between 25% and 30% of patients harbor occult
microscopic metastases that cannot be detected by CT
[10–14].
False-negative examinations are therefore inevitable, but the number of
false-negative examinations can be minimized by eliminating observer error and
recognizing the limitations of imaging. Historically, pitfalls in nodal
assessment, such as unopacified bowel loops and vascular anomalies, can be
overcome using a modern MDCT unit with multiplanar reformations (Figs.
6A,
6B,
6C, and
6D).
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Fig. 6A —24-year-old man with paraaortic relapse from undifferentiated
malignant teratoma (embryonal carcinoma) of testis. Contrast-enhanced MDCT
images show value of multiplanar reformations. Paraaortic node
(arrow) is not readily seen from adjacent bowel loops on axial
(A), sagittal (B), and coronal (C) images.
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Fig. 6B —24-year-old man with paraaortic relapse from undifferentiated
malignant teratoma (embryonal carcinoma) of testis. Contrast-enhanced MDCT
images show value of multiplanar reformations. Paraaortic node
(arrow) is not readily seen from adjacent bowel loops on axial
(A), sagittal (B), and coronal (C) images.
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Fig. 6C —24-year-old man with paraaortic relapse from undifferentiated
malignant teratoma (embryonal carcinoma) of testis. Contrast-enhanced MDCT
images show value of multiplanar reformations. Paraaortic node
(arrow) is not readily seen from adjacent bowel loops on axial
(A), sagittal (B), and coronal (C) images.
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Fig. 6D —24-year-old man with paraaortic relapse from undifferentiated
malignant teratoma (embryonal carcinoma) of testis. Contrast-enhanced MDCT
images show value of multiplanar reformations. Oblique coronal multiplanar
reformatted image shows left paraaortic node (arrow).
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Developments in imaging that may overcome limitations of CT in terms of
diagnosing involved lymph nodes include FDG PET and MRI with lymphotrophic
nanoparticles. The potential advantage of FDG PET over CT is that it is a
functional imaging technique that identifies metabolically active sites of
disease and thus provides different information from anatomic imaging. Studies
comparing FDG PET with CT in primary staging of GCT show that FDG PET is
useful for detecting viable tumor in lesions that are visible on CT and may
prevent false-positive diagnosis on CT in clinical stage II disease
[15]. However, FDG PET does
not improve staging in patients with clinical stage I disease because, similar
to CT, it is poor at detecting small-volume (i.e., subcentimeter) disease
[15,
16]. Furthermore, FDG PET is
not able to identify mature teratoma; therefore, FDG PET is not recommended in
the primary staging of testicular GCT
[4].
An alternative to CT for staging testicular GCT is MRI. Despite
developments in MRI with faster acquisitions, MRI is not routinely used for
staging, in part because of its longer examination times, higher cost, and
limited availability compared with CT. However, MRI is useful for the
detection and characterization of CNS disease as well as musculoskeletal and
hepatic metastases. MRI may also be valuable as a problem-solving technique in
the presence of equivocal CT findings.
In the detection of retroperitoneal lymph nodes, MRI is comparable with CT
and has the same important limitation—that is, the inability to identify
disease in normal-sized nodes or distinguish reactive from malignant enlarged
nodes. MRI with lymphotrophic nanoparticles has been shown to be an effective
method for evaluating lymph nodes in different cancers
[17–20].
Lymphatic targeting results from transcytosis of nanoparticles into the
interstitial space, from which they are transported to lymph nodes by
lymphatics. Within lymph nodes, these nanoparticles are internalized by
macrophages, resulting in intracellular trapping and changes in magnetic
properties. The results of a recent study of 18 patients with testicular
cancer showed that lymphotrophic nanoparticle–enhanced MRI has a higher
sensitivity (88%) and specificity (92%) for detecting nodal metastases than
MRI alone, which had a sensitivity and specificity of 71% and 68%,
respectively [18]. The role of
MRI with lymphotrophic nanoparticles needs to be evaluated in a large
prospective study.
Surveillance
In patients with stage I disease, surveillance after orchidectomy as a
management strategy is increasingly recognized as the preferred option
[21]. This is a result of a
growing awareness of long-term complications, with a twofold increase in
cardiovascular morbidity and a 10% excess lifetime risk of a second malignancy
in patients treated with radiotherapy, chemotherapy, or both after 30 years of
follow-up [22,
23]. Surveillance protocols
are designed to identify relapse at the earliest stage, thereby enabling
earlier treatment. Treatment at an early stage results in disease-free
survival rates of more than 98%, and in compliant patients, surveillance
should be considered the treatment option of choice.
In addition to clinical and serum marker assessments, imaging with CT forms
the basis of surveillance strategies, but the frequency of CT studies varies
greatly among centers. The potential benefit of repeated scanning must be
weighed against the financial and health costs of more frequent scanning. A
thoracic CT examination gives a radiation dose equivalent to 400 chest
radiographs (8 vs 0.02 mSv, respectively), whereas for CT of the chest and
abdomen, the dose is increased to approximately 20 mSv, which is a dose
equivalent to 1,000 chest radiographs. This radiation exposure results in a
1:1,000 lifetime risk of a second cancer and leukemia in a 25-year-old patient
over the subsequent 40 years.
Possible approaches to reducing radiation exposure are to use imaging with
nonionizing radiation or use low-dose CT techniques. First, using nonionizing
radiation imaging techniques, such as sonography and MRI, has been suggested
for surveillance programs. However, sonography is not as reliable as CT or MRI
in the assessment of abdominal paraaortic nodes. MRI and CT are equivalent in
terms of detecting malignant nodes because both rely on size criteria. In the
setting of testicular GCT, limited data suggest that MRI could replace CT for
the detection of abdominal disease
[24]. Alternatively, low-dose
CT techniques may be used to reduce radiation exposure; for example, the
results of a small study of 25 men showed that a low-dose CT examination
(minimum, 20 mA; maximum, 220 mA) and a standard-dose CT examination (minimum,
40 mA; maximum, 440 mA) were equivalent in identifying retroperitoneal
lymphadenopathy [25]. However,
both of these approaches—that is, MRI or low-dose CT
techniques—need to be validated in suitable surveillance protocols in
larger prospective trials.
In stage I nonseminomatous GCT, approximately 30% of patients will relapse;
thus, treating all patients would risk toxicity in more than 70% of the cases
[10,
13]. Vascular or lymphatic
invasion is the most powerful predictor of relapse. The absence of yolk sac
elements and the presence of undifferentiated cells are also adverse
independent prognostic variables. Relapse rates approach 50% in high-risk
patients compared with approximately 20% in those without high-risk factors.
In a large prospective study on surveillance in patients with nonseminomatous
GCT, 45% of the patients who relapsed did not have raised marker levels at the
time recurrent disease was discovered
[13]. Sixty-one percent of
relapses occurred in the paraaortic nodes and 10% in mediastinal or
supraclavicular nodes. Ninety-five percent of those who did relapse were in
the IGCCCG good prognostic group and overall survival free from GCT was 99%.
Approximately 80% of relapses occur within the first year after orchidectomy,
90% by year 2, and almost all by year 3 of surveillance
[13,
26]. Hence, the number of
scans should be greatest during the first year. Surveillance is performed
rigorously with clinical follow-up and serum marker analysis, and imaging of
the thorax and abdomen is routinely performed.
The value of chest CT compared with chest radiography has been studied. In
a series of 168 patients with stage I nonseminomatous GCT, surveillance chest
radiography, rather than chest CT, was performed
[27]. Twenty-five percent (42
patients) of the patients suffered a relapse, eight (19%) of whom relapsed
with chest disease [27]. Seven
of these latter eight patients had evidence of disease elsewhere that was
identified on abdominal CT. The one patient in that series who had only chest
disease at relapse was clearly diagnosed by chest radiography. These findings
led the authors to conclude that chest imaging with CT would not have changed
the prognosis of those with disease relapse in the chest
[27].
The role of pelvic CT has also been called into question. In one series of
patients with testicular GCT, pelvic lymphadenopathy was seen in 16 of 167
patients (9.6%) [28]. The
presence of bulky paraaortic lymphadenopathy was the only significant
predictor for pelvic disease and was present in 11 of 16 patients. Other risk
factors for pelvic disease include previous scrotal or inguinal surgery,
maldescent, tunica vaginalis invasion, and retroperitoneal lymph node
dissection. In the absence of these risk factors, routine pelvic CT for
patients on surveillance for stage I disease may constitute unnecessary
irradiation [28].
Centers vary in their preferences of surveillance protocols, but most
undertake abdominal CT between two and six times during the first year after
orchidectomy. To date, no consensus about the optimal strategy has been
reached, but centers that scan patients more frequently do not detect relapse
at a significantly earlier stage than those using less rigorous schedules.
Indeed, in one study of 46 patients, all relapses detected after the first
3-month CT examination were detected on the basis of clinical suspicion,
raised tumor marker levels, or findings on chest radiography
[29]. Furthermore, the results
of a recent prospective randomized trial of two versus five CT scans for
surveillance of patients with stage I nonseminomatous GCT showed no difference
in the outcomes of patients undergoing surveillance according to the five-scan
schedule compared with those undergoing surveillance according to the two-scan
schedule [30].
Is there a role for FDG PET in identifying patients suitable for
surveillance? Early studies in patients with nonseminomatous GCT suggested
that patients with negative findings on FDG PET were unlikely to relapse and
therefore did not require adjuvant treatment and could be monitored with
surveillance [31,
32]. However, this strategy
was not confirmed in a large prospective multicenter study that showed that
the relapse rate among patients with negative FDG PET findings remained high
[33]. Thus, FDG PET was not
able to identify patients suitable for surveillance.
For stage I nonseminomatous GCT, our surveillance protocols focus on the
first year, with the investigations reducing in intensity in subsequent years.
Serum marker levels are checked monthly for the first year, and chest
radiography, clinical examination, and CT of the abdomen only, unless the
pelvis is deemed high risk, are performed at 3 months and 1 year after
orchidectomy. This strategy is broadly similar to the recent NCCN guidelines
[6], although it reduces the
frequency of CT.
In cases of seminoma, wide-scale adoption of surveillance was limited until
recently, mainly because of the lack of a reliable serum tumor marker.
Furthermore, the predominant intraabdominal site of relapse meant that regular
cross-sectional imaging was needed. However, surveillance has recently been
popularized after publication of a new predictive model for relapse in stage I
seminoma: A multivariate analysis of patients from centers in Canada, the
United Kingdom, and Denmark identified tumor size (> 4 cm) and invasion of
the rete testis as significant predictors for relapse
[34]. In the absence of both
of these factors, patients were found to have no more than a 12% risk of
relapse, suggesting that there is a group of patients at particularly low risk
for whom surveillance might be an attractive option
[34].
Relapses are rare after 2 years but have been reported to occur up to 6
years after the initial diagnosis
[34,
35]. Most relapses are in the
paraaortic nodes, followed by mediastinal and supraclavicular nodes and lung
metastases [35,
36]. Only 30% of seminoma
relapses will be marker-positive. No studies have addressed the optimal
scanning or follow-up frequency, with policies differing widely among
institutions [21]. The policy
at our hospital is to perform abdominal CT and chest radiography every 6
months for the first 2 years after orchidectomy and image the pelvis only if
the patient has previously undergone pelvic surgery. Abdominal CT and chest
radiography are then performed annually until 5 years after the diagnosis.
Assessment of Tumor Response and Residual and Recurrent Disease
CT remains the primary imaging technique for assessing response to
treatment (Figs. 5A and
5B). Reduction in the size of
metastases is the main change on CT that indicates a positive response to
therapy even if malignant cells persist within the residuum. The CT findings
may parallel a reduction in serum marker levels, and performing interval CT
during therapy and after completion of therapy is important to assess response
[37]. In addition to aiding in
the assessment of tumor size, CT can help assess response and residual masses
after chemotherapy by depicting changes in appearance. Cystic change, which
can readily be assessed using CT, after chemotherapy is associated with mature
differentiated teratoma and may indicate the need for surgical removal because
these tumors may undergo malignant transformation
[2,
38,
39]. Imaging to assess
residual disease may allow selection of patients who may benefit from surgical
resection—traditionally, those with residual masses greater than 1 cm.
In patients with large-volume residual masses, CT and MRI may be useful in
planning the operative approach.
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Fig. 7B —60-year-old man with residual mass after undergoing
chemotherapy treatment for seminoma. Corresponding 18F-FDG PET
image shows no increased activity in residual mass (arrow).
Subsequent follow-up over 2 years has shown no evidence of recurrent
disease.
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Fig. 8A —52-year-old man previously treated for stage IV
nonseminomatous germ cell tumor had slowly rising tumor marker level but no
apparent disease on contrast-enhanced CT; 18F-FDG PET/CT images
were obtained. Fused color-coded FDG PET/CT images show increased uptake in
nodes. Uptake is seen in supraclavicular fossa (arrow, A) and
posterior mediastinum (arrow, B).
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Fig. 8B —52-year-old man previously treated for stage IV
nonseminomatous germ cell tumor had slowly rising tumor marker level but no
apparent disease on contrast-enhanced CT; 18F-FDG PET/CT images
were obtained. Fused color-coded FDG PET/CT images show increased uptake in
nodes. Uptake is seen in supraclavicular fossa (arrow, A) and
posterior mediastinum (arrow, B).
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Fig. 8C —52-year-old man previously treated for stage IV
nonseminomatous germ cell tumor had slowly rising tumor marker level but no
apparent disease on contrast-enhanced CT; 18F-FDG PET/CT images
were obtained. Fused color-coded FDG PET/CT images show increased uptake in
nodes. Small nodes (arrow) can in retrospect be seen on unenhanced CT
images through supraclavicular fossa (C) and mediastinum
(D).
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Fig. 8D —52-year-old man previously treated for stage IV
nonseminomatous germ cell tumor had slowly rising tumor marker level but no
apparent disease on contrast-enhanced CT; 18F-FDG PET/CT images
were obtained. Fused color-coded FDG PET/CT images show increased uptake in
nodes. Small nodes (arrow) can in retrospect be seen on unenhanced CT
images through supraclavicular fossa (C) and mediastinum
(D).
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Seminoma is extremely sensitive to chemotherapy and radiation therapy, so a
residual mass after treatment usually constitutes only fibrosis and necrosis.
However, identifying any residual disease is important because this mass will
need further treatment, usually surgery, and FDG PET may have a role in this
regard (Figs. 7A and
7B). The results of a large
prospective study, the SEMPET trial
[40], in which FDG PET was
used to assess residual tumors in patients with seminoma treated with
chemotherapy, showed that FDG PET was more accurate than other modalities for
assessment [40]. In that
study, FDG PET was performed in all patients with residual masses greater than
1 cm within 4–12 weeks of completion of chemotherapy. The results were
compared with histologic analysis of tumor viability or CT evidence of
progression. Those authors reported that FDG PET correctly identified all
cases of residual tumor in lesions greater than 3 cm and in 95% of residual
tumor in lesions less than 3 cm. These results gave an overall specificity and
sensitivity of 100% and 80%, respectively, for FDG PET compared with 74% and
70% for CT. Because there were no false-positive results, the authors
suggested that a positive FDG PET scan, even in small lesions, is highly
specific for tumor viability
[40]. However, the experience
described in an article by researchers at Indiana University is different
[41]. Those investigators
found in a retrospective review of 24 FDG PET scans that all negative scans
correlated with no viable disease and that all patients with residual disease
had positive FDG PET studies. On the other hand, four cases with positive
findings on FDG PET that led to surgical resections of residual masses
revealed only fibrosis, necrosis, or inflammation (i.e., false-positives).
They sug gested that a negative FDG PET scan indicates a low likelihood of
persistent seminoma after chemotherapy, whereas a positive PET scan does not
translate into a similar high probability of persistent seminoma
[41].
In patients with residual masses after undergoing chemotherapy for
nonseminomatous GCT, FDG PET use is limited because mature differentiated
teratoma has variable low uptake or no uptake and cannot be distinguished from
fibrosis or necrosis
[42–44].
Patients with residual mature differentiated teratoma require surgery because
there is a risk of the mass undergoing malignant transformation. The crucial
decision in this setting is whether the response requires surgery, and FDG PET
is unable to help in this regard.
Detection of recurrent disease relies on careful follow-up with a
combination of clinical assessment, serum marker analysis, chest radiography,
and abdominal CT. Follow-up protocols vary depending on the type of tumor,
stage, treatments given, and individual institutions. They are based on the
known patterns of disease relapse in testicular GCT
[6,
45]. FDG PET has been
investigated in the detection of recurrent disease and may have a role in
patients with raised tumor markers but no active disease on other imaging
examinations such as CT (Figs.
8A,
8B,
8C, and
8D). In a series of 47 scans
obtained for the assessment of residual masses (18 with raised markers) and 23
scans for the investigation of raised markers in the presence of normal CT
findings, the authors found that all but one of the FDG PET scans that were
positive identified disease
[43]. Furthermore, negative
scans were not as predictive of absence of disease, with five false-negative
scans, but in three of these patients a subsequent FDG PET scan was positive,
and FDG PET scans were the first imaging technique to identify the site of
recurrence. Therefore, in the presence of raised marker levels and negative
imaging findings, including negative FDG PET, the most appropriate follow-up
imaging may be to repeat FDG PET.
Summary
As the management of testis cancer moves toward less aggressive treatment
for patients with a good prognosis, imaging strategies are continuing to be
evaluated and modified to make the most efficient use of imaging and to reduce
radiation burden in this group of young patients. However, CT remains central
to the selection of management decisions, with MRI and FDG PET being used in
certain clinical situations (Fig.
9).
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Abstract
Introduction
