2017 Section 7 Green Book

Review Clinical Review & Education

Use of FDG-PET/CT in Oropharyngeal Squamous Cell Carcinoma

Figure 4. Therapy Assessment

A

B

C

sponse. The lower the pretreatment SUV value, themore response to chemotherapywas seen. 1 Ameta-analysis demonstrated that PET is highly accurate for response monitoring or relapse detection af- ter radiotherapy with or without chemotherapy in advanced head and neck cancers. This study showed 94% sensitivity, 82% speci- ficity, 75% positive predictive value, and 95% negative predictive value for PET in detecting residual lesions. 38 Sjovall et al 39 evalu- ated 82 patients with head and neck cancer (85% OPSCC) and re- portedthatPET/CThasasensitivityandspecificityof100%and78%, respectively, in detecting residual tumor after radiotherapy. The other issue is the optimal timing to evaluate the treatment responsewith PET. Although on one handwe shouldwait for radia- tion therapy and chemotherapy to show their full effect and treat- ment inflammation to decrease (8-10 weeks), on the other, we do not want to wait too long to prevent tumor progression or missed treatment opportunities. Sensitivity of PET in therapy assessment is lowwhenperformed less than 10weeks after treatment, whereas specificity seems not to be related to timing. 38 Most reports stud- ied the capability of PET in treatment evaluation within 2 months after therapy. 23 Kimet al 40 reported high negative predictive value of PET on evaluation of radiotherapy after 1 month. However, PET used later than 12 weeks after treatment can decrease the number of diagnosticneckdissections needed. 41 Ingeneral, it seems that PET is a good modality for therapy assessment of OPSCC approxi- mately3monthsafterradiotherapyand/orchemotherapy( Figure4 ). Role of PET in Recurrence Detection of OPSCC Despite all advances in treatment methods (surgery, radiotherapy, chemotherapy), the locoregional recurrence rate of HPV-negative OPSCC remains high. Some articles claim that up to 24% of pa- tients with advanced head and neck cancer developed locore- gional recurrence. 23 Although most of the time when the recur- rence is detected, it is advanced and has aggressive tumor characteristics (eFigures 2 and 3 in the Supplement ), a recent study A, Axial fused positron emission tomography/computed tomography (PET/CT) image of initial scan of a man in his 60s with a history of left tongue base squamous cell carcinoma, which presented as a fludeoxyglucose-avid lesion (standard uptake value, 9.99) (arrowhead) in PET/CT. The patient was treated with chemoradiation (9 weeks cetuximab, 7000 cGy). B, Three months after

treatment, PET/CT scan showed good response with diffuse uptake suggestive of postradiotherapy inflammation (diffuse uptake, standard uptake value, 6.74). C, The 9-month follow-up PET/CT showed complete response without any interval treatment.

by Fakhry et al 42 showed improved survival in patients with recur- rent HPV-related OPSCC treated with salvage surgery. In recur- rence detection, PET has a lower false-negative and false-positive rate when compared with conventional imaging. 43 A meta- analysis by Isles et al 38 showed that PET has a sensitivity and speci- ficity of 94%and 82%, respectively, for detecting residual or recur- rent head and neck cancer. In a study that compared PET/CT vs whole-body MRI in detecting recurrence in oropharyngeal and hy- popharyngeal SCC, PET/CT had higher accuracy. 44 Positron emis- sion tomography was reported to be a powerful tool in early recur- rence detection of OPSCC 23 (eFigure 4 in the Supplement ). Role of PET in Prognosis of OPSCC Some studies evaluated the role of PET in predicting prognosis of OPSCC and showed that a negative PET/CT result after therapy is associated with lower chance of recurrence and better prognosis. Therefore, this subgroup of patients needs less frequent radiologic surveillance. The effect of negative PET result ismore prominent in HPV-positive patients and is a better predictor of survival than OP- SCC stage for these patients. 45 Different studies evaluated the relationship between PET parameters (SUV max, SUV mean, SUV peak , TLG,MTV)andprognosticfactorssuchasdisease-freesurvival(DFS), progression-free survival (PFS), overall survival (OS), and disease- specific survival (DSS). Because of its observer-independent mea- surement, SUV is a popular PET parameter used by multiple scientists. 46 Some previous studies claimthat SUV max predicts head andneckcanceroutcomeandhigherSUV max isassociatedwithworse DFS. 13 Most of these studies evaluated tumors from various head and neck sites, with different tumor characteristics, risk factors, and different overall prognosis. However, several recent studies re- ported that SUVhadpoor predictiveperformance for treatment out- come andhadno independent relation toOSorDFS, especiallywhen corrected for stage. 13,46 Overall, it should not be a valuable predic- tive factor for prognosis. 3,46

(Reprinted) JAMA Otolaryngology–Head & Neck Surgery January 2016 Volume 142, Number 1

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