Sivarajah S, et al. - Researchers compared accuracies of the initial posttreatment positron emission tomography and computed tomography (PET-CT) for evaluation of oropharyngeal squamous cell carcinoma treatment outcome and recurrence. They also defined the indicators of false-positive findings. Among patients treated with primary surgery vs nonsurgical management, a higher specificity in fludeoxyglucose F 18–labeled PET-CT for initial posttreatment surveillance imaging was indicated in the findings. Close evaluation for possible residual or recurrent disease was suggested in both sets of patients with posttreatment FDG PET–CT findings with an SUVmax greater than 5.0.

Methods

• In this retrospective cohort study, authors identified adults newly diagnosed with oropharyngeal squamous cell carcinoma who received treatment with curative intent from October 1, 2006 through November 30, 2016, using the Alberta Cancer Registry (n=380).
• They included patients (n=190) who underwent PET-CT within 1 year of treatment completion; out of these, a total of 103 patients (54.2%) had PET-CT findings positive for residual or recurrent disease, and 61 (32.1%) had false-positive findings.
• Forty-two (68.9%) among the 61 patients, received chemoradiotherapy (CRT) and 19 (31.1%) had primary surgery.
• True-positive findings, indicating a prevalence rate of disease of 22.1% were seen in 42 patients.
• They analyzed the data from July through October 2017.
• The exposures included 1 of 2 primary treatment modalities (surgery with or without adjuvant therapy vs CRT).
• Posttreatment FDG PET-CT was seen in all patients.
• The diagnostic odds ratio, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of PET-CT for detecting residual and/or recurrent disease were included in the primary outcome measures.
• Indicators of false-positive findings were determined by a multivariate analysis.
• They evaluated the discriminative ability using receiver operating characteristic curve analysis of maximum standardized uptake value (SUVmax) metabolic data.

Results

• As per data, out of the 190 participants, 77.9% were men, with a mean (SD) age at diagnosis of 58.5 (8.5) years.
• Findings suggested that the diagnostic odds ratio was 19.3 (95% CI, 5.7-65.1); pooled sensitivity, 93.3% (95% CI, 80.7%-98.3%); and pooled specificity, 57.9% (95% CI, 49.4%-66.0%).
• For primary surgery, the PPV of detecting disease was 54.7% (95% CI, 38.8%-69.8%) and 31.1% (95% CI, 20.2%-44.4%) for CRT.
• For primary surgery, the NPV was 100% (95% CI, 94.7%-100%) and 96.6% (95% CI, 89.5%-99.1%) for CRT.
• Multivariate analysis treatment type, p16 disease, and smoking status were identified by multivariate analysis as indicative of false-positive findings.
• The optimal cutoff SUVmax for indicating true- vs false-positive results in the receiver operating characteristic curve analysis for primary tumors, was 5.1 for surgically treated patients (area under the curve, 0.729; 95% CI, 0.570-0.888) and 5.3 for patients treated with CRT (area under the curve, 0.844; 95% CI, 0.700-0.989).