No Evidence That PET and PET/CT Has Advantages in Screening for Ovarian Cancer

Because of the lack of relevant research, there is currently no substantial evidence that patients with ovarian cancer can benefit from positron emission tomography (PET) imaging alone or in combination with computed tomography (CT) imaging. As regards diagnostic accuracy, in certain cases, recurrences can be detected earlier and more accurately with PET or PET/CT than with conventional imaging techniques.

This is the conclusion of the final report by the German Institute for Quality and Efficiency in Healthcare (IQWiG; Cologne), which was published on May 23, 2012. Ovarian cancer is the fifth most common malignant tumor in women. Every year 15.9 women in every 100,000 are diagnosed with the disease in Germany and it claims the lives of eight in 100,000 women per year. Since the ovaries lie deep in the abdomen and an ovarian tumor typically causes no symptoms for a long time, it is frequently only discovered at a late stage.

Many medical experts hope that a study utilizing PET or PET/CT alone or in combination with other modalities would be better able to distinguish between benign and malignant tumors when ovarian cancer is suspected. It could also help categorize cancerous tumors into the accurate stage, make it easier to assess whether they respond to treatment and to show earlier and with greater certainty, whether a recurrence or secondary tumor (metastasis) has occurred. This information should then enable patients to be given better treatment recommendations.

IQWiG therefore searched the international literature for studies investigating the effects of diagnosis using PET or PET/CT on health aspects of direct relevance to patients. For example, the results of this research--and an appropriately personalized treatment--could contribute to patients having better chances of survival, spare them unnecessary operations or other diagnostic procedures, or improve their quality of life. However, the search for such studies was unsuccessful, so the question as to the patient-relevant benefit of PET or PET/CT had to remain unanswered.

PET can better detect recurrences in certain cases. Moreover, IQWiG searched for studies in which the diagnostic accuracy and prognostic power of PET or PET/CT were compared with other diagnostic methods. The basic question is how often a PET investigation gives a correct result. On the one hand, it should overlook true, cancerous tumors as rarely as possible, but on the other, it should not awake any false suspicions.

The results of a total of 40 individual studies on this topic were evaluated. However, these studies permit a robust conclusion only in respect of the detection (or exclusion) of a recurrence, where PET or PET/CT appears to be more effective than other methods. Nevertheless, it is still unclear whether this only applies to patients in whom symptoms (e.g., pain) have already occurred, or also to those in whom routine screening has shown an abnormal blood test result. This is because only very few studies give exact information on this point.

Since even these patients have not been studied to determine whether the higher-assess accuracy of PET or PET/CT has positive effects on mortality, the burden of disease or the quality of life, IQWiG assumes that a patient-relevant benefit of PET or PET/CT is not proven. For instance, it is particularly questionable whether a recurrence detected by PET or PET/CT can actually be better treated--and the patient thereby has a noticeable advantage.

Therefore, it is imperative that doctors fully inform their patients not only of the possible benefits in the form of an earlier diagnosis, but also of the possible hazards. The latter can arise from an earlier start to second-line treatment associated with considerable side effects, but not with a prolongation of survival. Therefore, studies are urgently needed to assess the patient-relevant benefit of PET or PET/CT in the diagnosis of ovarian cancers in direct comparison with conventional diagnostic techniques.

IQWiG published the early findings in the form of the preliminary report in July 2011 and interested parties were invited to submit comments. When the commenting procedure ended, the preliminary report was revised and sent as a final report to the contracting agency, the Federal Joint Committee (G-BA), in March 2012. 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.

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German Institute for Quality and Efficiency in Healthcare