High methodological quality studies of PET in malignant melanoma patients needed

Robust studies are lacking / IQWiG calls for comparative studies of high methodological quality

The relevance of positron emission tomography (PET) alone or in combination with computed tomography (CT) in patients with malignant melanoma cannot be currently assessed due to a lack of meaningful studies. This is the result of a final report published by the German Institute for Quality and Efficiency in Health Care (IQWiG) on 20 July 2011.

Hidden metastases are often detected too late

Malignant melanoma ("black skin cancer") may follow very different courses. In most patients the tumour can be removed completely by minor surgery. However, on first diagnosis some patients already have hidden metastases that are often detected only at a later stage. Many health care experts hope that an examination with PET or PET/CT, alone or in combination with other methods, can help detect hidden metastases as early as the first diagnosis. In addition, they hope that in follow-up examinations, PET or PET/CT can detect tumour recurrence earlier. The information obtained should then enable doctors to provide better treatment recommendations for patients.

Benefit for patients is crucial

IQWiG therefore searched the international scientific literature for studies investigating the impact of PET or PET/CT on health aspects directly relevant to patients. For example, the test results could help treat patients with further useful therapies at an earlier stage, or the results could help spare patients unnecessary treatment. However, the search for such studies was unsuccessful, so that the question as to the benefit of PET or PET/CT remained unanswered.

Reliability not clear

In addition, IQWiG searched for studies in which the diagnostic accuracy of PET or PET/CT was compared to other test methods. This investigates the question as to how often a PET test produces wrong results. The test should on the one hand overlook metastases as rarely as possible, but on the other, should not raise unjustified suspicions. Although a total of 17 diagnosis accuracy studies were found, the diagnostic accuracy of PET or PET/CT varied greatly in these studies. A comparison of PET or PET/CT with other technologies (e.g. CT alone) was investigated in only 2 studies, so that no general conclusions can be drawn for this question either.

Studies of high methodological quality are therefore urgently needed to investigate the benefit of PET or PET/CT in patients with malignant melanoma.

Procedure of report production

IQWiG published the preliminary results in the form of a preliminary report in December 2010 and interested parties were invited to submit comments. When the comments stage ended, the preliminary report was revised and sent as a final report to the contracting agency, the Federal Joint Committee, in May 2011. The written comments were published in a separate document at the same time as the final report. The report was produced in collaboration with external experts.