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treatment have consistently found that the accuracy of the scans
varies with timing, with a longer time interval associated with a
greater accuracy.
48-51
Our study confirms these findings, with
scans for local or regional disease performed after 12 weeks
having a greater specificity (
P
= .009 and
P
= .004, respec-
tively), but no difference in sensitivity, when compared with
those performed before 12 weeks. These results are slightly dif-
ferent from 2 previous meta-analyses that demonstrated an
improvement in sensitivity, rather than specificity, with a delay
of 10 to 12 weeks after the completion of treatment before scan-
ning. However, both of these meta-analyses included retrospec-
tive as well as prospective studies in their analysis.
The lower specificity in the immediate posttreatment
period found in our review is likely related to the increased
vascularity, edema, and inflammatory changes at the pri-
mary site and in the neck after (chemo)radiation, which
results in an increased physiological uptake of FDG
52
and
hence more false-positive readings. However, a deliberate
delay before the first posttherapy scan is not without conse-
quences; a prolonged period between the completion of che-
motherapy and salvage surgery allows time for extensive
postradiation fibrosis to develop, leading to an increased fre-
quency and severity of surgical complications.
53
In deter-
mining the optimal time for the initial scan, we must
therefore balance the need for prompt diagnosis and man-
agement of disease against the risk of misleading results if
scans are performed too early. However, the timing of the
first posttreatment scan remains somewhat controversial
despite numerous diagnostic accuracy studies. Based on the
results of our review, we would support a delay of 12 weeks
after (chemo)radiotherapy before imaging because of the
improvement in diagnostic accuracy seen with a later scan.
Strengths and Limitations
There are several strengths of this meta-analysis. We included
only prospective studies in our review, thus reducing the
number of articles included in our study compared with previ-
ous meta-analyses. However, this inclusion may help reduce
the risk of bias that may be found with retrospective studies.
Because studies with positive results are more likely to be pub-
lished, there is always the risk of publication bias with sys-
tematic reviews. We attempted to minimize the potential for
such bias by using a comprehensive search strategy with no
language restrictions. Our exclusion of conference abstracts,
letters, editorials, and gray literature may affect the results;
however, we believe that this would have minimal impact
overall. Publication bias was detected for the nodal sites only,
and based on the large fail-safe number (
.
1000), we believe
it is highly unlikely that these studies would have not been
found using our comprehensive search strategy.
The studies identified in our review had some limitations.
Most notably, the reference standard was not consistent
across all studies; histopathology was performed in every
patient in only 4 of the 27 included studies. In most cases,
histopathological confirmation was used only in patients
with a positive PET or PET/CT because of the invasive
nature of biopsies and neck dissections. Clinical follow-up,
with and without conventional imaging, formed the basis of
the reference standard in those with negative PET scans.
This may potentially result in the overestimation of test sen-
sitivity and underestimation of test specificity.
54
There was also substantial variability in the sensitivity and
specificity estimates among studies. Although the difference in
imaging modality and timing explained this to some extent,
some heterogeneity remained despite subgroup analysis. Other
variables such as the stage and location of the tumor at initial
diagnosis, the reference standard used, and the clinical presen-
tation at recurrence may have contributed to the heterogeneity
among studies. We could not assess the impact of these factors
on test accuracy because of inconsistent reporting of data.
Conclusion
This is a meta-analysis focused on the diagnostic accuracy
of PET and PET/CT for the detection of residual and/or
recurrent local and regional disease and distant metastases
in patients with HNSCCs using only prospective data. We
found that both modalities had a good overall diagnostic
accuracy for detection of residual and/or recurrent disease at
local, nodal, and distant sites, with PET/CT being more
specific than PET alone for the detection of disease at the
primary site. The accuracy of visual assessment and semi-
quantitative analysis of images were comparable at local,
nodal, and distant sites. The timing of the scan had an
impact on accuracy, with later scans being more specific
than earlier scans. This study has determined that the most
ideal strategy for follow-up scans is after 12 weeks post-
treatment with the use of combined PET and CT.
Author Contributions
Phylannie K. F. Cheung
, study concept and design, acquisition of
data, analysis and interpretation of data, drafting of the manuscript,
critical revision of the manuscript for important intellectual con-
tent, and statistical analysis;
Ronald Y. Chin
, study concept and
design, analysis and interpretation of data, drafting of the manu-
script, critical revision of the manuscript for important intellectual
content, and study supervision;
Guy D. Eslick
, study concept and
design, analysis and interpretation of data, drafting of the manu-
script, critical revision of the manuscript for important intellectual
content, statistical analysis, and study supervision.
Disclosures
Competing interests:
None.
Sponsorships:
None.
Funding source:
None.
Supplemental Material
Additional supporting information may be found at
http://otojournal .org/supplemental.
References
1. Curado MP, Hashibe M. Recent changes in the epidemiology
of head and neck cancer.
Curr Opin Oncol
. 2009;21:194-200.
2. Marur S, Forastiere AA. Head and neck cancer: changing epi-
demiology, diagnosis, and treatment.
Mayo Clinic Proc
. 2008;
83:489-501.
Otolaryngology–Head and Neck Surgery 154(3)
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