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PET imaging changed clinical management in two thirds of cases and eliminated the need for additional tests and procedures in 70%

PET imaging of bladder cancer changed clinical management in two thirds of cases and eliminated the need for additional tests and procedures in 70%, according to a small clinical series reported here.

In almost 60% of the cases, FDG-PET revealed disease that was either more extensive or less extensive than indicated by CT or MRI, Andrea B. Apolo, M.D., of Memorial Sloan-Kettering Cancer Center in New York, said at the Genitourinary Cancers Symposium.

PET's performance versus standard imaging modalities for bladder cancer "makes it a candidate for standard-of-care management for metastatic disease," said Dr. Apolo.

Few studies had evaluated the utility of PET in the management of bladder cancer. Sensitivity and specificity have remained undefined, and no one had determined whether PET provides incremental information unavailable with CT or MRI, Dr. Apolo said.

To assess the performance of PET in bladder cancer, investigators prospectively enrolled 57 patients with urothelial cancer in the National Oncology PET Registry at Sloan-Kettering. All the patients had baseline CT/MRI imaging and FDG-PET/CT imaging.

Four patients underwent PET imaging for initial staging, 12 for treatment response, and 41 for suspected recurrence.

Physicians completed registry questionnaires before and after PET/CT imaging, and the answers were compared to determine how PET/CT imaging affected patient management.

Lesions identified by PET/CT were retrospectively validated by biopsy or serial imaging.

Lesion analysis showed PET imaging had an overall sensitivity of 88%, ranging from 83% for liver lesions to 100% for soft tissue, adrenal, and kidney lesions. Overall specificity was 91%, including 80% for lymph nodes and adrenals and 100% for all other sites.

A patient-based analysis of accuracy revealed an overall sensitivity of 80% and specificity of 94%. The figures were derived from follow-up imaging studies or biopsy, and PET/CT demonstrated comparable accuracy by both validation methods, said Dr. Apolo.

A comparison with original CT and MRI imaging results showed that PET/CT findings differed in a majority of cases. PET/CT showed more extensive disease in 40% of cases and less extensive disease in 18%.

The PET/CT results changed clinical management in 36 of the 57 patients. PET imaging negated the need for biopsy in 11 patients, avoided additional imaging in 11, and changed the diagnosis from organ-confined to metastatic disease in 10 patients.

In three cases, initial plans to observe patients were changed to immediate treatment, and in one case, planned local radiation therapy was changed to chemotherapy.

"I think PET/CT is a good tool to use [as an adjunct] when baseline MRI and CT are done," said Dr. Apolo. "Those provide anatomical interpretation of the extent of disease, and PET/CT has more resolution."

"The majority of patients in this study were undergoing PET/CT for suspected recurrence," she added. "It would apply more to these types of patients, when there is a suspicion of disease."

Source: ASCO GU