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Diagnostic accuracy of 18 FDG PET-CT for evaluation of malignancy in anterior mediastinal

lesions – the DECiMaL study

C. Proli (1), P. De Sousa (1), S. Jordan (1), V. Anikin (1), A. Devaraj (1), S.M. Love (2), M.

Shackcloth (2), N. Kostoulas (3), K. Papagiannopoulos (3), Y. Haqzad (4), M. Loubani (4), F.

Sellitri (5), F. Granato (5), A. Bush (6), A. Marchbank (6), S. Iyer (7), M. Scarci (7), E. Lim (1) on

behalf of the UK Thoracic Surgery Research Collaborative

(1) Royal Brompton & Harefield NHS Foundation Trust, London, UK; (2) Liverpool Heart and

Chest Hospital NHS Foundation Trust; (3) Leeds Teaching Hospitals NHS Trust; (4) Hull and

East Yorkshire Hospitals NHS Trust, UK; (5) Royal Devon and Exeter NHS Foundation Trust,

UK (6) Plymouth Hospitals NHS Trust, UK, (7) Papworth Hospital NHS Foundation Trust, UK

Corresponding Author:

Mr Eric Lim

Academic Division of Thoracic Surgery

The Royal Brompton Hospital

Sydney Street

London SW3 6NP

United Kingdom

Tel: +44 (0)207 351 8591

Fax: +44 (0)207 351 8560

Email: [email protected]

Word count: 1554

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Abstract

Objectives: The aim of this study is to collate multi-institutional data to determine the value

by defining diagnostic performance of FDG-PET/CT for malignancy in patients undergoing

surgery with an anterior mediastinal mass in order to ascertain the clinical utility of PET/CT

to differentiate malignant from benign aetiologies in patients presenting with an anterior

mediastinal mass

Setting: DECiMaL Study is a multicentre, retrospective, collaborative cohort study in seven

UK surgical sites.

Participants: Between January 2002 and June 2015 a total of 134 patients were submitted

with a mean age (SD) of 55 years (16) of which 69 (51%) were men. We included all patients

undergoing surgery who presented with an anterior mediastinal mass and underwent

PET/CT. PET/CT was considered positive for any reported avidity as stated in the official

report and the reference was the resected specimen reported by histopathology using WHO

criteria.

Primary and secondary outcome measures: Sensitivity, specificity, positive and negative

predicted values of [18F]-FDG PET in determining malignant aetiology for an anterior

mediastinal mass.

Results: The sensitivity and specificity of PET/CT to correctly classify malignant disease were

83% (95% CI 74-89) and 58% (37-78). The positive and negative predictive values were 90%

(83-95) and 42% (26-61%).

Conclusions: The results of our study suggests reasonable sensitivity but no specificity

implying that a negative PET/CT is useful to rule out the diagnosis of malignant disease

whereas a positive result has no value in the discrimination between malignant and benign

disease of the anterior mediastinum.

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Strengths and limitations of this study

-� To our knowledge this is the largest study to date (essential to ensure narrow

confidence intervals for estimates) versing this subject

-� We were able to obtain an estimate of test performance relatively quickly through

an established research collaborative

-� The study did not include the entire spectrum of the anterior mediastinal masses, in

particular the small masses that were only kept under surveillance or discharged.

Funding statement

This research received no specific grant from any funding agency in the public, commercial

or not-for-profit sectors.

Competing interests statement

All authors declare no conflicts of interest. Outside this work, Eric Lim reports personal fees

from Abbott Molecular, personal fees from Glaxo Smith Kline, personal fees from Pfizer,

personal fees from Novartis, personal fees from Covidien, personal fees from Roche,

personal fees from Lily Oncology, personal fees from Boehringer Ingelheim, personal fees

from Medela, grants and personal fees from ScreenCell, personal fees from Ethicon, outside

the submitted work; and is the founder of Informative Genomics, a blood based molecular

diagnostic company in London.

Data sharing statement

Anonymised individual patient data that underlie the results reported in this article will be

available to researchers who provide a methodologically sound proposal. Proposals should

be directed to the corresponding author.

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Contributorship statement

CP, PDS and EL designed the work, acquired and analysed data and drafted the work; EL

interpreted the data; SJ, VA, AD, SML, MS, NK, KP, YH, ML, FS, FG, AB, AM, SI, MS acquired

and analysed data, revised the work critically; all authors approved the version to be

published and agreed to be accountable for all aspects of the work in ensuring that

questions related to the accuracy or integrity of any part of the work are appropriately

investigated and resolved.

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Introduction

Abnormalities in the anterior mediastinum are often discovered as an incidental finding.

When detected, often present as a diagnostic challenge as few radiological features are

sufficiently discriminatory to guide clinicians on the best course of management. One of the

principal considerations is the probability of malignancy, as the perceived risk of cancer

guides the recommendation for invasive tissue sampling or excision. Although PET/CT is

widely used in this regard, little is known on the diagnostic and clinical test performance of

18-F fluorodeoxyglucose positron emission tomography [18F]-FDG PET-CT as no large

published series have been reported in the literature.

The aim of our study is to determine the diagnostic accuracy by defining the sensitivity and

specificity of 18

FDG PET-CT scans to identify malignancy in patients who have presented with

an anterior mediastinal mass.

Methods

We conducted a UK wide multi-centre retrospective study under the auspices of the UK

Thoracic Surgery Research Collaborative. Formal application was made to the Research

Ethics Committee (15/SS/0185) and the outcome was that the study did not require NHS

ethics review.

We included patients who have undergone surgery for an anterior mediastinal abnormality

and received 18

FDG PET-CT as part of their pre-operative work up. We excluded patients in

whom a formal histological diagnosis was not obtained or did not have a formal 18

FDG PET-

CT report.

Consecutive patients from January 2002 to June 2015 were identified from 7 participating

institutions of the UK Thoracic Surgery Research Collaborative through interrogation of

electronic records. As a pragmatic study, the index test of 18

FDG PET-CT was conducted by

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Consultant Radiologists and Nuclear Medicine Physicians according to UK Royal College of

Radiologists recommendations[1]. A positive test result was defined as a formally worded

“positive” uptake for the anterior mediastinal mass. The reference standard was the

histology of the resected anterior mediastinal mass as conducted by Pathologists in

accordance to the UK Royal College of Pathologists guidelines and reported according to

WHO criteria. Malignancy was defined in accordance to what would influence surgical

management including thymic carcinoma, thymoma, lymphoma, and any other malignant

tumours, and the following diseases were classified as non-malignant: thymic hyperplasia,

thymic cyst, and “no malignancy” as per histology report.

As the study was undertaken retrospectively, we know that the results of the histopathology

(reference test) would not be available for the readers of the 18

FDG PET-CT (index test) as

surgical resection only occurs after the pre-operative investigations. We also have no reason

to believe that the reporting pathologists would have access to the pre-operative 18

FDG PET-

CT reports.

Categorical data will be summarised as frequency (%), continuous data will be summarised

as mean (SD) or median (IQR) as appropriate to the data distribution. The primary outcome

is the calculated sensitivity, specificity, positive and negative predictive values with

corresponding 95% confidence intervals. We specified a-priori estimates around 50% would

be considered none, around 75% moderate and around 100% to have excellent clinical test

performance and favour interpretation on sensitivity and specificity (considered robust

estimates) rather than positive or negative predictive values (that can be altered by disease

prevalence).

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We estimate a sample size of 70 patients based on estimated sensitivity of 0.90 with a

lowest acceptable confidence interval of 0.75 using sample size calculations detailed by

Flahault et al [2]. Statistical analyses were conducted on Stata 13 (College Station, Texas,

USA).

Results

From January 2002 and June 2015, a total of 672 patients were included of which 521 were

excluded due to not having a PET-CT and 17 excluded due to not having radiology report,

leaving 134 patients for analysis (figure 1). The mean age (SD) was 55 (16) years of which 69

(51%) were men. The baseline and demographic characteristics of the cohort are

summarised in table 1.

Of the 134 patients 110 had a positive and 24 had a negative 18

FDG PET-CT report. A

malignant diagnosis was reported in 101 and a non-malignant diagnosis in 33 patients (table

2).

The sensitivity and specificity of PET-CT to correctly classify malignant disease for anterior

mediastinal masses were 83% (95% CI 74 to 89) and 58% (37 to 78) respectively and the

corresponding positive and negative predictive values were 90% (83 to 95) and 42% (26 to

61%) respectively (table 2).

Discussion

The results of our study, to our knowledge is the largest to date (essential to ensure narrow

confidence intervals for estimates) suggests that 18

FDG PET-CT is moderately useful to rule

out the diagnosis of malignancy when the test result is negative (good sensitivity), however

is not able to rule in the diagnosis of malignancy when the result is positive.

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Once an anterior mediastinal mass is diagnosed on imaging, downstream management is

predicated on the risk of malignancy to stratify patients for management, with high risk

patients assigned to invasive biopsy or surgery, intermediate risk patients assigned to

surveillance and low risk patients assigned to discharge. In a recent survey up to 50% of

centres reported the use of PET for this purpose.

In cohort series, it was reported that thymic tumours represent 50% of anterior mediastinal

lesions, followed by lymphomas (25%) and less commonly a mixture of other aetiologies

such as teratoma[3]. A definitive diagnosis can only be achieved after invasive biopsy[4] or

surgical resection. The reported specificity of fine needle aspiration is limited (57-

82%)[5][6][7] and the diagnostic value of computerised tomography (CT) and positron

emission tomography (PET) are not well known as few studies have been conducted and

with sample sizes are very small, typically less than 60[8]. Decisions regarding direct surgical

resection of anterior mediastinal masses can be challenging as the morphological features of

thymic lesions overlap and a definite differentiation between histologic subtypes of thymic

pathology by CT can be difficult[9][10]. Previous studies have shown promising results for

SUVmax values in the differentiation between malignant and benign lesions[11].

With moderately high sensitivity, the results from our study suggest that 18

FDG PET-CT has

moderate utility to ruling out malignancy in patients where the test is negative. There is still

an appreciable proportion (17%) test negative despite the presence of disease. From a

clinical perspective it remains to individual judgement whether this is an acceptable

proportion balances against the consequences of missing a potentially invasive tumour.

It is difficult to define the clinical utility when faced with an “abstract” figure for sensitivity of

83%, to help clinicians understand how this would fit in the clinical setting, it would be

pertinent to look at more developed guidelines on perceived clinical utility of 18

FDG PET-CT

for the solitary pulmonary nodule to assess cancer risk. The results from a 2008 meta-

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analysis [12] reported a sensitivity of 95% for PET to diagnose malignancy in pulmonary

nodules, considerably higher than 83% for anterior mediastinal mass. Despite higher levels

of sensitivity, there is still a reluctance for experts to discharge a patient with a negative

18FDG PET-CT, as in the 2013 ACCP guidelines [13] the authors recommended serial CT

monitoring when the 18

FDG PET-CT despite low clinical probability of lung cancer.

Currently, there are no established risk models for malignancy in anterior mediastinal

masses, and therefore numeric quantification of risk is not possible. In the circumstance

where the pre-test probability for malignancy is very low (e.g. if the CT appearance suggests

diffuse enlargement of the thymus only) then it would be reasonable to reassure the patient

(a negative 18

FDG PET-CT would not alter clinical management). If the pre-test probability is

very high (e.g. a large lobulated mass in anterior mediastinum) it would be reasonable to

proceed to invasive biopsy or resection (a negative 18

FDG PET-CT would not reassure). In the

most difficult subgroup where the pre-test probability for malignancy is intermediate, given

than serial CT imaging is recommended for lung cancer (despite sensitivity of 95%) then it

would be reasonable to default to the time tested method of screening for growth by CT for

anterior mediastinal masses as well. If that is the case, then there is clearly no clinical utility

for 18

FDG PET-CT (a negative test does not prevent serial CTs and a positive test is not

reliable to rule in malignancy).

The limitations of our study, aside from that associated with retrospective conduct is that

we did not include the entire spectrum of the anterior mediastinal masses, in particular the

small masses that were only kept under surveillance or discharged. On the other hand, we

have included the larger lesions that are more worrying and in whom 18

FDG PET-CT is usually

requested. We were able to obtain an estimate of test performance relatively quickly

through an established research collaborative as prospective conduct of a validation study is

likely to require significant funding, more centres and time as anterior mediastinal lesions

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are not common. Certainly we would welcome and encourage international efforts to

address this important issue, ideally with reference of clinical and cost effectiveness.

Conclusions

18FDG PET-CT is moderately useful to rule out the diagnosis of malignancy when the test

result is negative (good sensitivity), however is not able to rule in the diagnosis of

malignancy when the result is positive (poor specificity). At the existing levels of sensitivity a

negative test is insufficient to reassure and obviate the need for serial CT surveillance of

indeterminate masses in the anterior mediastinum. Therefore, we conclude that 18

FDG PET-

CT does not have a role in routine clinical practice to assess the malignant potential of an

anterior mediastinal mass.

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Figure 1 – Flow diagram (STARD)

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Table 1 - Demographic characteristics of the cohort and diagnosis classification as per

histology report

(n=134)

Mean age (SD) 55 (16)

Male, n (%) 69 (51)

Histology

Benign, n (%) 33 (25)

Thymic hyperplasia 10 (8)

Thymic cyst 8 (6)

No malignancy 15 (11)

Malignant, n (%) 101 (75)

Thymoma 55 (41)

Other malignant tumours 38 (28)

Thymic carcinoma 8 (6)

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Table 2 – Diagnostic test performance for PET-CT evaluation of malignancy in an anterior

mediastinal mass

18

FDG PET-CT positive 18

FDG PET-CT negative

Benign histology 19 14

Malignant histology 91 10

Test performance (with 95% CI)

Sensitivity 82.7 74.3 to 89.3

Specificity 58.3 36.6 to 77.9

Positive predictive value 90.1 82.5 to 95.1

Negative predictive value 42.4 25.5 to 60.8

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References

1 The Royal College of Radiologists. The Royal College of Radiologists PET-CT in the UK.

2005.

http://www.bnms.org.uk/~bnms/images/stories/downloads/documents/rcr_petct_fi

nal.pdf

2 Flahault A, Cadilhac M, Thomas G. Sample size calculation should be performed for

design accuracy in diagnostic test studies. J Clin Epidemiol 2005;58:859–62.

doi:10.1016/j.jclinepi.2004.12.009

3 Liu Y. Characterization of thymic lesions with F-18 FDG PET-CT: an emphasis on

epithelial tumors. Nucl Med Commun 2011;32:554–62.

doi:10.1097/MNM.0b013e328345b984

4 Luzzi L, Campione A, Gorla A, et al. Role of fluorine-flurodeoxyglucose positron

emission tomography/computed tomography in preoperative assessment of anterior

mediastinal masses. Eur J Cardio-thoracic Surg 2009;36:475–9.

doi:10.1016/j.ejcts.2009.03.055

5 Assaad MW, Pantanowitz L, Otis CN. Diagnostic accuracy of image-guided

percutaneous fine needle aspiration biopsy of the mediastinum. Diagn Cytopathol

2007;35:705–9. doi:10.1002/dc.20738

6 Desai F, Shah M, Patel S, et al. Fine needle aspiration cytology of anterior mediastinal

masses. Indian J Pathol Microbiol;51:88–

90.http://www.ncbi.nlm.nih.gov/pubmed/18417872 (accessed 14 Nov 2016).

7 Powers CN, Silverman JF, Geisinger KR, et al. Fine-needle aspiration biopsy of the

mediastinum: A multi-institutional analysis. Am J Clin Pathol 1996;105:168–

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8 Ahn JM, Lee KS, Goo JM, et al. Predicting the histology of anterior mediastinal

masses: comparison of chest radiography and CT. J Thorac imaging 1996;11:265–


9 Treglia G, Sadeghi R, Giovanella L, et al. Is 18F-FDG PET useful in predicting the WHO

grade of malignancy in thymic epithelial tumors? A meta-analysis. Lung Cancer.

2014;86:5–13. doi:10.1016/j.lungcan.2014.08.008

10 Kaira K, Sunaga N, Ishizuka T, et al. The role of [18

F]fluorodeoxyglucose positron

emission tomography in thymic epithelial tumors. Cancer Imaging 2011;11:195–201.

doi:10.1102/1470-7330.2011.0028

11 Tatci E, Ozmen O, Dadali Y, et al. The role of FDG PET/CT in evaluation of mediastinal

masses and neurogenic tumors of chest wall. Int J Clin Exp Med 2015;8:11146–52.

12 Cronin P, Dwamena BA, Kelly AM, et al. Solitary pulmonary nodules: meta-analytic

comparison of cross-sectional imaging modalities for diagnosis of malignancy.

Radiology 2008;246:772–82. doi:10.1148/radiol.2463062148

13 Gould MK, Donington J, Lynch WR, et al. Evaluation of individuals with pulmonary

nodules: When is it lung cancer? Diagnosis and management of lung cancer, 3rd ed:

American college of chest physicians evidence-based clinical practice guidelines.

Chest 2013;143:e93S–120S. doi:10.1378/chest.12-2351

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Section & Topic No Item Reported on page #

TITLE OR ABSTRACT

1 Identification as a study of diagnostic accuracy using at least one measure of accuracy

(such as sensitivity, specificity, predictive values, or AUC)

1

ABSTRACT

2 Structured summary of study design, methods, results, and conclusions

(for specific guidance, see STARD for Abstracts)

2

INTRODUCTION

3 Scientific and clinical background, including the intended use and clinical role of the index test 5

4 Study objectives and hypotheses 5

METHODS

Study design 5 Whether data collection was planned before the index test and reference standard

were performed (prospective study) or after (retrospective study)

5

Participants 6 Eligibility criteria 5

7 On what basis potentially eligible participants were identified

(such as symptoms, results from previous tests, inclusion in registry)

5

8 Where and when potentially eligible participants were identified (setting, location and dates) 5

9 Whether participants formed a consecutive, random or convenience series 5

Test methods 10a Index test, in sufficient detail to allow replication 5

10b Reference standard, in sufficient detail to allow replication 6

11 Rationale for choosing the reference standard (if alternatives exist) 6

12a Definition of and rationale for test positivity cut-offs or result categories

of the index test, distinguishing pre-specified from exploratory

6

12b Definition of and rationale for test positivity cut-offs or result categories

of the reference standard, distinguishing pre-specified from exploratory

6

13a Whether clinical information and reference standard results were available

to the performers/readers of the index test

6

13b Whether clinical information and index test results were available

to the assessors of the reference standard

6

Analysis 14 Methods for estimating or comparing measures of diagnostic accuracy 6

15 How indeterminate index test or reference standard results were handled 6

16 How missing data on the index test and reference standard were handled 6

17 Any analyses of variability in diagnostic accuracy, distinguishing pre-specified from exploratory 6

18 Intended sample size and how it was determined 7

RESULTS

Participants 19 Flow of participants, using a diagram 7, figure 1

20 Baseline demographic and clinical characteristics of participants 7, table 1

21a Distribution of severity of disease in those with the target condition 7, table 2

21b Distribution of alternative diagnoses in those without the target condition 7, table 2

22 Time interval and any clinical interventions between index test and reference standard N/A

Test results 23 Cross tabulation of the index test results (or their distribution)

by the results of the reference standard

7

24 Estimates of diagnostic accuracy and their precision (such as 95% confidence intervals) 7, table 2

25 Any adverse events from performing the index test or the reference standard N/A

DISCUSSION

26 Study limitations, including sources of potential bias, statistical uncertainty, and generalisability 8

27 Implications for practice, including the intended use and clinical role of the index test 6-8

OTHER

INFORMATION

28 Registration number and name of registry N/A

29 Where the full study protocol can be accessed N/A

30 Sources of funding and other support; role of funders 3

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A diagnostic cohort study on the accuracy of 18-Fluoro-Deoxy-Glucose (18FDG)Positron

Emission Tomography- Computer Tomography (PET-CT) for evaluation of malignancy in

anterior mediastinal lesions – the DECiMaL study










Mr Eric Lim



Sydney Street

London SW3 6NP

United Kingdom

Tel: +44 (0)207 351 8591

Fax: +44 (0)207 351 8560


Word count: 1554

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2

Abstract





mediastinal mass


UK surgical sites.






criteria.



mediastinal mass.



(83-95) and 42% (26-61%).





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3








Funding statement















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4








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5

Introduction









The aim of our study was to determine the diagnostic accuracy by defining the sensitivity

and specificity of 18

FDG PET-CT scans to identify malignancy in patients who have presented

with an anterior mediastinal mass.

Methods




ethics review.


and received 18



FDG PET-

CT report.





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6










As the study was undertaken retrospectively, we assumed the results of the histopathology





FDG PET-

CT reports (although they may have had access to this inform on the request forms).

Categorical data were summarised as frequency (%), continuous data summarised as mean

(SD) or median (IQR) as appropriate to the data distribution. The primary outcome is the

calculated sensitivity, specificity, positive and negative predictive values with corresponding

95% confidence intervals. We specified a-priori estimates around 50% would be considered

none, around 75% moderate and around 100% to have excellent clinical test performance

and favour interpretation on sensitivity and specificity (considered robust estimates) rather

than positive or negative predictive values (that can be altered by disease prevalence). We

also conducted secondary analysis of receiver operator characteristics curve analyses to

explore the influence of SUVmax (where available) on the diagnosis of malignancy.

We estimated a sample size of 70 patients based on estimated sensitivity of 0.90 with a


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7


USA).

Results



leaving 134 patients for analysis (figure 1). The mean age (SD) was 55 (16) years (with a

range of 18 to 88 years) of which 69 (51%) were men. The baseline and demographic

characteristics of the cohort are summarised in table 1.




2).





Data from SUVmax were available in 96 patients and the calculated ROC area under the

curve was 0.63 (95% CI 0.45 to 0.79) (Figure 2).

Discussion






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8






In published cohort series, it was reported that thymic tumours represent 50% of anterior

mediastinal lesions, followed by lymphomas (25%) and less commonly a mixture of other

aetiologies such as teratoma[3]. A definitive diagnosis can only be achieved after invasive

biopsy[4] or surgical resection. The reported specificity of fine needle aspiration is limited

(57-82%)[5][6][7] and the diagnostic value of computerised tomography (CT) and positron






SUVmax values in the differentiation between malignant and benign lesions[11]. However,

the results of our analyses suggested that discrimination by SUVmax was relatively poor.


FDG PET-CT has








FDG PET-CT

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9







FDG PET-CT is negative despite low clinical probability of lung cancer.





(a negative 18






that serial CT imaging is recommended for lung cancer (despite sensitivity of 95%) then it



for 18










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10




Conclusions






FDG PET-



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11


histology report

(n=134)


Male, n (%) 69 (51)

Histology

Benign, n (%) 33 (25)


Thymic cyst 8 (6)



Thymoma 55 (41)



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12


mediastinal mass

18


FDG PET-CT negative








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Figure 2 – ROC plot of SUVmax versus malignancy

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14

References


2005.


nal.pdf



doi:10.1016/j.jclinepi.2004.12.009



doi:10.1097/MNM.0b013e328345b984




doi:10.1016/j.ejcts.2009.03.055



2007;35:705–9. doi:10.1002/dc.20738





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15








2014;86:5–13. doi:10.1016/j.lungcan.2014.08.008




doi:10.1102/1470-7330.2011.0028










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TITLE OR ABSTRACT



1

ABSTRACT



2

INTRODUCTION



METHODS



5




5








6



6



6



6






RESULTS








7



DISCUSSION



OTHER

INFORMATION




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Page 1 of 18


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A diagnostic cohort study on the accuracy of 18-Fluoro-Deoxy-Glucose (18FDG)Positron

Emission Tomography- Computer Tomography (PET-CT) for evaluation of malignancy in

anterior mediastinal lesions – the DECiMaL study










Mr Eric Lim



Sydney Street

London SW3 6NP

United Kingdom

Tel: +44 (0)207 351 8591

Fax: +44 (0)207 351 8560


Word count: 1554

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2

Abstract





mediastinal mass


UK surgical sites.






criteria.



mediastinal mass.



(83-95) and 42% (26-61%).





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3








Funding statement















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4








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5

Introduction









The aim of our study was to determine the diagnostic accuracy by defining the sensitivity

and specificity of 18

FDG PET-CT scans to identify malignancy in patients who have presented

with an anterior mediastinal mass.

Methods




ethics review.


and received 18



FDG PET-

CT report.





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6










As the study was undertaken retrospectively, we assumed the results of the histopathology





FDG PET-

CT reports (although they may have had access to this inform on the request forms).

Categorical data were summarised as frequency (%), continuous data summarised as mean

(SD) or median (IQR) as appropriate to the data distribution. The primary outcome is the

calculated sensitivity, specificity, positive and negative predictive values with corresponding

95% confidence intervals. We specified a-priori estimates around 50% would be considered

none, around 75% moderate and around 100% to have excellent clinical test performance

and favour interpretation on sensitivity and specificity (considered robust estimates) rather

than positive or negative predictive values (that can be altered by disease prevalence). We

also conducted secondary analysis of receiver operator characteristics curve analyses to

explore the influence of SUVmax (where available) on the diagnosis of malignancy.

We estimated a sample size of 70 patients based on estimated sensitivity of 0.90 with a


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7


USA).

Results



leaving 134 patients for analysis (figure 1). The mean age (SD) was 55 (16) years (with a

range of 18 to 88 years) of which 69 (51%) were men. The baseline and demographic

characteristics of the cohort are summarised in table 1.




2).





Data from SUVmax were available in 96 patients and the calculated ROC area under the

curve was 0.63 (95% CI 0.45 to 0.79) (Figure 2).

Discussion






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8






In published cohort series, it was reported that thymic tumours represent 50% of anterior

mediastinal lesions, followed by lymphomas (25%) and less commonly a mixture of other

aetiologies such as teratoma[3]. A definitive diagnosis can only be achieved after invasive

biopsy[4] or surgical resection. The reported specificity of fine needle aspiration is limited

(57-82%)[5][6][7] and the diagnostic value of computerised tomography (CT) and positron






SUVmax values in the differentiation between malignant and benign lesions[11]. However,

the results of our analyses suggested that discrimination by SUVmax was relatively poor.


FDG PET-CT has








FDG PET-CT

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9







FDG PET-CT is negative despite low clinical probability of lung cancer.





(a negative 18






that serial CT imaging is recommended for lung cancer (despite sensitivity of 95%) then it



for 18










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10




Conclusions






FDG PET-



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11


histology report

(n=134)


Male, n (%) 69 (51)

Histology

Benign, n (%) 33 (25)


Thymic cyst 8 (6)



Thymoma 55 (41)



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12


mediastinal mass

18


FDG PET-CT negative








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Figure 2 – ROC plot of SUVmax versus malignancy

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14

References


2005.


nal.pdf



doi:10.1016/j.jclinepi.2004.12.009



doi:10.1097/MNM.0b013e328345b984




doi:10.1016/j.ejcts.2009.03.055



2007;35:705–9. doi:10.1002/dc.20738





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15








2014;86:5–13. doi:10.1016/j.lungcan.2014.08.008




doi:10.1102/1470-7330.2011.0028










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TITLE OR ABSTRACT



1

ABSTRACT



2

INTRODUCTION



METHODS



5




5








6



6



6



6






RESULTS








7



DISCUSSION



OTHER

INFORMATION




Page 19 of 18


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Documents

BMJ Open is committed to open peer review. As …...BMJ Open is committed to open peer review. As part of this commitment we make the peer rev iew history of every article we publish