Benefits of PET or PET/CT Imaging Unproven in Recurrent Bowel Cancer

For patients with a suspected recurrence of bowel cancer, recent available study data allow no clear conclusions as to the advantages and disadvantages of utilizing positron emission tomography (PET) imaging, either alone or in combination with computed tomography (CT).

These findings are resulted from the fact that there no studies have directly compared the benefits of these imaging techniques in recurrent colorectal carcinoma (bowel cancer) with traditional diagnostic techniques. Although PET or PET/CT show a higher diagnostic accuracy (i.e., in specific instance), recurrences can be detected more effectively, it is still not clear how this actually affects patient-relevant outcomes such as quality of life. This was the conclusion of the final report of the German Institute for Quality and Efficiency in Health Care (IQWiG; Cologne, Germany), published on October 24, 2012.

Bowel cancer is the second most common cancerous tumor in both men and women. Yearly, more than 65,000 people are diagnosed with the disease in Germany and more than 25,000 die from it annually. Approximately 80% of the recurrences occur in the first two years after surgery for bowel cancer. After five years, virtually no more recurrences were detected. These can occur at the original site—the bowel—or as secondary tumors (metastases), for example, in the liver. Follow-up after surgery should therefore continue for five years.

Many specialists hope that when a recurrence is suspected, using PET or PET/CT scanning alone or in combination with other methods is better able to differentiate between benign and malignant tumors (recurrence diagnostics) and, if confirmed, to categorize the stage of malignant tumors appropriately ( i.e., to determine how advanced the cancer is [recurrence staging]). This information should provide patients with better treatment recommendations.

IQWiG searched the international literature for studies that had examined the consequences of a diagnostic intervention using PET or PET/CT on health aspects of direct pertinence to patients. For example, the diagnostic investigation findings--and suitably customized treatment--could contribute to better chances of survival for patients, save them from unnecessary operations or additional diagnostic interventions, or improve their quality of life.

For the preliminary report, IQWiG had already made an additional search for studies in which the diagnostic accuracy and prognostic capacity of PET or PET/CT had been compared with other diagnostic techniques. This referred to the question as to how frequently a PET study provides a correct finding.

The findings of a total of five evidence syntheses and 13 individual studies regarding this question could be assessed. The conclusion on recurrence detection was that PET and PET/CT appear capable of detecting or excluding recurrences more effectively than a traditional diagnostic intervention consisting solely or mostly on CT findings. This applies especially to local recurrences and distant metastases. It is not possible to state with conviction whether PET and PET/CT vary in terms of their diagnostic accuracy.

Significant questions in relation to PET technology remain unresolved. It has not yet been studied, for example, whether the higher accuracy of PET or PET/CT has a positive effect on mortality, the burden of disease, or quality of life. As long as this lack of data remains, a patient-relevant benefit of PET or of PET/CT as an adjunct to a suspicion-driven diagnostic study with traditional modalities is not validated. For instance, it is particularly not known whether a recurrence detected by using PET or PET/CT can actually be better treated and thereby generate a noticeable advantage for patients. Experts are therefore keenly awaiting the results of a Canadian study with more than 400 patients, which is to be published shortly.

Stefan Lange, the deputy director of IQWiG, commented on the new data gleaned by IQWiG during the evaluation procedure of the study on laparotomies, “The fact that the only benefit study on PET turned out to be unsuitable is extremely regrettable. The rupture of the logical link between diagnosis and treatment devalued the study results.”

As Mr. Lange explained, a fundamental principle of medicine is that a diagnostic intervention is only of benefit if it enables patients to receive more customized treatment.

Related Links:
German Institute for Quality and Efficiency in Health Care