2017 Section 7 Green Book

that reported exclusively on residual/recurrent disease at the

primary site and 5 studies on residual/recurrent disease at

the neck only. There were no prospective studies that evalu-

ated the detection of distant metastases exclusively; all 3

studies included in our analysis for distant disease also

reported on residual/recurrent disease at the primary site

and in the neck.

We found that FDG-PET and FDG-PET/CT had a high

overall accuracy in detecting local, nodal, and distant resi-

dual/recurrent disease after (chemo)radiotherapy in patients

initially diagnosed with HNSCCs. The pooled sensitivity,

specificity, PPV, and NPV for local and regional residual/

recurrent disease were similar to the findings of previous

meta-analyses. Gupta et al

reported a sensitivity of 79.9%

and 72.7%, specificity of 87.5% and 87.6%, PPV of 58.6%

and 52.1%, and NPV of 95.1% and 94.5% for primate site

and nodal recurrences, respectively. Similarly, a systematic

review by Isles et al

that included data from dual-head

gamma cameras reported a sensitivity of 94% and 74%, spe-

cificity of 82% and 88%, PPV of 75% and 49%, and NPV

of 95% and 96% for local and regional recurrent disease,

respectively. For the detection of distant metastases in

recurrent head and neck cancers, not specifically SCCs, Gao

et al

reported a sensitivity of 92% and a specificity of

95%.

Our results indicated that the overall diagnostic accuracy

was slightly lower for the detection of residual and recurrent

disease in the neck, when compared with detection at pri-

mary, distant, or multiple sites considered together. The

lower sensitivity of PET for nodal disease compared with

other sites may be related to the spectrum of disease in the

studies that reported on regional recurrence; nearly a third

of these studies included only patients in whom nodal dis-

ease was present at initial diagnosis. Micrometastases in the

lymph nodes may not be detected by imaging, leading to a

higher false-negative rate and lower sensitivity.

The pooled NPVs for residual and recurrent disease at

local, nodal, distant, and all sites combined were nevertheless

quite high, suggesting that PET and PET/CT scans can reliably

exclude residual/recurrent locoregional disease and distant

metastases. A negative posttreatment scan can therefore guide

the ongoing management of patients with HNSCCs and poten-

tially reduce the need for more invasive diagnostic procedures.

PET/CT has largely superseded the use of PET alone in

clinical practice, and we wanted to explore whether this

newer technology would have an impact on the test diagnos-

tic accuracy. We found that there was a small benefit of

PET/CT over PET alone for the detection of residual/recur-

rent disease but only at the primary site (

.001). The

results of our subgroup analyses suggest that PET/CT has

greater specificity, but no difference in sensitivity, when

compared with PET alone for the detection of local recur-

rences. We found no significant difference between the ima-

ging modalities in terms of sensitivity or specificity in the

detection of residual/recurrent nodal disease.

The increased specificity with PET/CT for the identifica-

tion of recurrent disease at the primary site may be related

to the improvement in anatomical localization possible with

the co-registration of anatomical and functional information.

Our results differ from the findings of a previous meta-

analysis by Gupta et al,

which showed no difference

between PET and PET/CT in terms of diagnostic perfor-

mance. While there were no prospective studies directly

comparing the use of PET/CT and PET in head and neck

cancers, the few retrospective studies directly comparing the

use of the 2 modalities generally reflect the findings of our

study. Fakhry et al

compared the use of PET and PET/CT

in 32 patients who presented with a suspicion of recurrent

HNSCC. They found no difference in sensitivity (94% for

both modalities) and a nonsignificantly higher specificity

for PET/CT (57% vs 36%-50%), and they concluded that

PET/CT was more accurate than PET alone. Likewise, a

study by Ishitaka et al

involving 129 patients with sus-

pected head and neck (including thyroid) cancer recurrence

demonstrated no significant sensitivity benefit of PET/CT

over PET (sensitivity 93.9% vs 91.4%, respectively) but a

significant improvement in specificity when integrated PET/

CT is used (specificity 97.2% vs 74.4%). Similarly, when

Chan et al

compared the use of the 2 modalities in 67

patients with papillomavirus-associated oropharyngeal

SCCs, the findings showed that PET/CT had a better NPV

compared with PET alone (98.2%-95% vs 95.7%-100%) for

the detection of nodal recurrence. On the other hand, a

study by Halpern et al

in patients with suspected local

recurrence found that integrated PET/CT did not signifi-

cantly improve the detection of recurrence compared with

PET alone.

FDG uptake by tissues can be assessed qualitatively

using visual comparison of the abnormal and normal tissue

or semiquantitatively through the calculation of standardized

uptake values (SUVs). While results indicated that there

was a trend toward a greater sensitivity or specificity with

the use of semiquantitative methods for image assessment,

the difference was not statistically significant at the primary

site or in the neck, suggesting that either method can be

used to interpret PET scans with a reliable degree of

accuracy.

This is consistent with a previous study

that suggested

that the accuracy of visual interpretation by an experienced

nuclear physician is comparable to SUV-based assessments.

While the calculation of SUV may be viewed as a more

objective index in assessing the uptake of FDG, it is never-

theless affected by technical aspects such as the uptake time

and the selection of the region of interest.

Moreover,

despite 3 of the included studies

21,27,29

nominating a spe-

cific cutoff value for diagnostic purposes, it has been argued

that such thresholds are somewhat arbitrary because of the

considerable overlap in SUVs between patients with benign

and malignant lesions.

While many institutions report

SUVs as part of their protocol, based on the results of our

study, visual assessment alone is sufficient for characteriz-

ing residual/recurrent HNSCCs.

Retrospective studies directly comparing the diagnostic

accuracy of PET and PET/CT at different time points after

Cheung et al