Prevalence of additional primary malignancies detected incidentally on PET/CT.

Dear Editor,

We entirely agree with the conclusions of Tibana et al.([1]). Although false-positives can occur with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT), the prevalence of true-positives cannot be underestimated. Additional primary malignancies may often be identified by this means and the likelihood of cure is much increased if such malignancies are treated promptly and aggressively. It was unclear what is the actual prevalence of malignancies discovered with PET/CT in this study.

The prevalence of additional malignancies discovered with PET/CT was highlighted in the various systems for breast([2]), bowel([3]), prostate([4]) and thyroid([5]) lesions. For example, in a study of 1665 patients, 70 incidentally detected lesions in the colon were identified and eventually 10 were diagnosed with bowel carcinoma([3]). There were additional pre-malignant lesions identified and early treatment was warranted in this scenario. Thus, it was found the prevalence of malignant and pre-malignant findings in the PET population was about 1.3%. A similar series showed a lower number of carcinomas but more adenomas (which would, of course, be considered pre-malignant) in a slightly larger series([6]). Hence, the prevalence was similar (at 1.1%). Knowing the prevalence may give a better idea of the importance of the incidental findings. This would be very helpful for both managing the individual patient as well as for public health and population health purposes.