Two modalities are better than one: PET/CT IDs distant malignancies

Whole-body PET/CT has demonstrated excellent diagnostic performance for the detection of distant malignancies, according to a meta-analysis of medical literature published online ahead of print in the Journal of Nuclear Medicine.

The hybrid imaging modality was shown to be particularly effective at detecting distant malignancies in patients with head and neck cancer, breast cancer and lung cancer, according to Guozeng Xu, MD, of the First Affiliated Hospital of Guangxi Medical University, Nanning, China, and colleagues.

“Early detection of distant malignancies in cancer patients is crucial for guiding subsequent staging procedures and treatment,” wrote the authors, who noted the limitations of using either conventional imaging or functional imaging alone. Chest x-ray, CT and other conventional imaging methods can’t reliably detect small distant lesions, while PET imaging alone has poor spatial resolution.

Integrated PET/CT, however, has been studied as a way of compensating for these issues, and Xu and colleagues conducted an analysis of studies about whole-body PET/CT for the detection of distant malignancies. A total of 41 studies were identified in the MEDLINE and EMBASE databases, collectively including more than 4,300 patients.

Overall results showed the sensitivity and specificity of whole-body PET/CT to be 0.93 and 0.96, respectively. A subgroup analysis conducted by the authors showed the sensitivity and specificity of whole-body PET/CT for various cancers, respectively, were as follows:

 - Head and neck cancer: 0.90 and 0.95

 - Lung cancer: 0.91 and 0.96

 - Breast cancer: 0.97 and 0.95

 - Cancer of the digestive system: 0.92 and 0.97

Since likelihood ratios are considered to be more clinically meaningful, according to Xu and colleagues, both positive likelihood ratios (PLRs) and negative likelihood ratios (NLRs) were used as measures of diagnostic accuracy. The authors explained there is no absolute cutoff, but a good diagnostic test may have PLRs greater than 10.0 and NLRs less than 0.1. The PLR for whole-body PET/CT was 20.7. “This value may be high enough to diagnose distant malignancies in cancer patients.”

Likewise, the NLR for whole-body PET/CT was 0.08, meaning a negative whole-body PET/CT result alone could justify ruling out distant malignancies in cancer patients, according to the authors.

Xu and colleagues suggested large, multicenter, prospective studies with standard PET/CT protocols to further investigate the added value of whole-body PET/CT over conventional imaging.