Correspondence (letter to the editor): More Reliance on PET-CT Findings

It is commendable that the authors have highlighted the combination of positron-emission tomography and computed tomography (PET-CT) in their article (1) and I do not see any conflict of interest with the sponsor. However, I think that the benefits derived from an additional work-up with computed tomography (CT) and magnetic resonance imaging (MRI) to follow-up PET findings are usually overrated. PET-CT by itself should already have considerable weight.

Radiography (2) plays a very important role when it comes to interpreting PET findings in patients with bone metastases—whether the radiograph provides an overview of the anatomical area or targets a special detail under fluoroscopy guidance. Any error may be fatal—this also applies to patients with metastases. Above all, conventional X-ray tomography (in the hands of an experienced radiologist) should be part of the work-up of unclear local findings, as it can provide exceptional insights. CT scans completely fail to visualized early rip metastases, and also with regard to the specificity of the findings—the same is true for MRI.

To monitor treatment response—according to EORTC and PERCIST criteria (version 1.1) (3), i.e. based on the standardized uptake value (SUV)—PET-CT has also to be performed using the proper tracer, i.e. as an ¹⁸F-fluoride PET, and, if necessary, without additional administration of an X-ray contrast agent. Small lesions may otherwise be masked. False-positive and false-negative CT and MRI findings may have serious consequences. In addition, MRI not only fails to detect focal osteolytic lesions. The CT scan is mainly required to establish the location of the PET findings. All of the above statements exclusively refer to the work-up of bone metastases. Radiation therapists (and their patients) would benefit from relying far less on CT and MRI findings.