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Timing of Post-TX Imaging Key in Head, Neck Cancer

Wed, Feb 22, 2012

Oral Cancer News

Source: MedScape Today


The investigators report on a systematic review and meta-analysis of 51 studies involving 2335 patients with head and neck squamous cell carcinoma who underwent post-treatment or surveillance with 18F-fluorodeoxyglucose (FDG) PET or FDG-PET/CT. The random-effects model-weighted mean pooled sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for detection of residual disease at the primary tumor site were 79.9% (95% CI, 73.7%-85.2%), 87.5% (95% CI, 85.2%-89.5%), 58.6% (95% CI, 52.6%-64.5%), and 95.1% (95% CI, 93.5%-96.5%), respectively. The respective values for detection of residual post-treatment neck nodes were 72.7% (95% CI, 66.6%-78.2%), 87.6% (95% CI, 85.7%-89.3%), 52.1% (95% CI, 46.6%-57.6%), and 94.5% (95% CI, 93.1%-95.7%).

In a subgroup analysis on timing of PET after completion of therapy, scans performed after 12 weeks had significantly higher diagnostic performance than scans done within 12 weeks, but only for residual neck nodes and not for residual disease at the primary tumor site. No statistically significant difference in diagnostic accuracy was noted between stand-alone PET and PET/CT.


Well-performed systematic reviews and meta-analyses are important contributions to the literature.[1] In this meta-analysis, the diagnostic performance of dedicated PET and PET/CT with FDG was investigated by pooling the data from a relatively large cohort of patients with head and neck cancer who had been treated with chemoradiation. The pooled evidence demonstrated good diagnostic performance for FDG-PET and FDG-PET/CT, regardless of the type of scanner, with very high NPV but somewhat suboptimal PPV; this is due to the nonspecificity of FDG, which also accumulates in inflammatory, infectious, and healing sites.

The timing of post-treatment FDG-PET or FDG-PET/CT may affect the overall PPV, but the optimal timing of scanning after completion of therapy has not been determined. The investigators noted that when timing is included as a covariate, the diagnostic performance for detection of residual neck nodes improved significantly when the interval after completion of therapy was 12 weeks or longer (P < .001). The weighted mean pooled sensitivity increased from 62.5% for time < 12 weeks to 90.4% for time ≥ 12 weeks. Similarly, the weighted mean pooled specificity increased from 85.1% for time < 12 weeks to 94.3% for time ≥ 12 weeks. In the absence of other available objective data, this meta-analysis demonstrates that it is probably reasonable to delay post-treatment PET to after 12 weeks from completion of chemoradiation in patients with head and neck cancer.

This news story was resourced by the Oral Cancer Foundation, and vetted for appropriateness and accuracy.

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