ORLANDO—The use of 18F- 2-deoxyglucose positron emission tomography plus computed tomography (FDG-PET/ CT) provides diagnostic information that enhances the clinical management of bladder cancer patients over CT or magnetic resonance imaging (MRI) alone, researchers reported here at the Genitourinary Cancers Symposium.
In a study of 57 patients with urothelial cancer, FDG-PET/CT changed the management of 68% of cases, reported Andrea B. Apolo, MD, a medical oncology fellow at Memorial Sloan-Kettering Cancer Center.
“FDG-PET/CT has an excellent sensitivity and specificity in the detection of metastatic bladder cancer. It avoided further testing and procedures, making it a candidate for standard-of-care management of metastatic disease,” she said during an oral abstract session at the meeting, which is cosponsored by the American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Urologic Oncology.
In some cases, patients scheduled for surgery “didn't have it because metastases were found. In other cases, patients planned for biopsy didn't have it because of the findings on PET.
“While it's hard to definitively state that one small study is practice-changing, we believe FDG-PET/CT at least warrants consideration in the management of patients with metastatic bladder cancer,” Dr. Apolo told OT.
“You should still perform CT and MRI at baseline as that provides anatomic data. But FDG-PET/CT then gives you a metabolic picture, telling you the extent of metastasis.”
Study Fills Void
Prior to this study, few studies had evaluated the utility of FDG-PET/CT in the management of bladder cancer. “Its sensitivity and specificity and impact on medical decisions were unclear,” Dr. Apolo said.
To investigate the accuracy and performance of FDG-PET/CT in bladder cancer, the researchers studied patients with urothelial cancer who were prospectively enrolled in the National Oncology PET Registry (NOPR) at Sloan-Kettering between May 2006 and February 2008. “We see almost 2,400 bladder cancer patients a year, and only 57 underwent PET over the nearly two-year period,” she noted.
The bladder was the primary site of the cancer in 51 patients; the renal pelvis, in six patients. Forty eight patients had Stage II-IV disease, 27 had received chemotherapy, and 10 had undergone radiation therapy.
In all 57 cases, FDG-PET/CT was performed after a baseline CT or MRI scan. Seventy-two percent of patients underwent PET imaging for restaging or suspected recurrence, 21% for initial staging, and 7% for monitoring treatment response.
A total of 46 patients with 133 lesions were evaluable; the rest were lost to follow-up, death, hospice care, or a return to their primary physician.
The lesions found on FDG-PET/CT were retrospectively validated either by biopsy or follow-up imaging. Then, two types of correlations were performed: An organ-specific, lesion-based analysis and a patient-based analysis.
Excellent Specificity, Sensitivity
The lesion-based analysis revealed that FDG-PET/CT had an overall sensitivity of 88%, ranging from 83% for liver lesions to 100% for soft tissue, adrenal, and kidney lesions. The overall specificity was 91%, ranging from 80% for lymph node and adrenal lesions to 100% for all other evaluable sites (lung, bone, liver, soft tissue, and kidney lesions). Thyroid and bladder lesions were excluded from the analysis.
In the patient-based analysis, the overall sensitivity and specificity of FDG-PET/CT were 80% and 94%, respectively.
The researchers then compared FDG-PET/CT results with those of the baseline CT and MRI scans to determine the impact of the FDG-PET/CT results on the management of bladder cancer patients.
FDG-PET/CT revealed more extensive disease in 40% of cases and less extensive disease in 18% of patients. In 32% of cases, the results were similar; the other 10% were lost to follow-up.
The FDG-PET/CT results changed the clinical management of 68% of patients. PET imaging negated the need for biopsy in 21% of patients, avoided additional imaging in 21%, and changed the diagnosis from organ-confined to metastatic disease in 19% of patients.
In 6% of cases, the initial plans for surveillance were changed to active treatment based on the FDG-PET/CT results. One patient, who had been scheduled for local radiation therapy, instead underwent systemic chemotherapy for more advanced disease based on the PET results.
Cost a Big Issue
While the afternoon session ran over, leaving no time for a formal question-and-answer period, about 20 oncologists patiently waited to ask Dr. Apolo questions afterward. The subject of most of the questions: The cost of the procedure, she said.
“It's a big issue, as Medicare, Medicaid, and other insurers are not yet covering FDG-PET/CT for bladder cancer,” Dr. Apolo said, adding that the scans cost about $3,000 to $5,000.
Howard M. Sandler, MD, Chair of the Department of Radiation Oncology at the Samuel Oschin Comprehensive Cancer Institute at Cedars-Sinai Medical Center, said that he hopes the study results encourage more insurance companies to cover the cost of FDG-PET for bladder cancer when appropriate.
“PET scans have been carefully regulated by payors to make sure they are used only when needed,” he said. “This abstract provides a reason to order FDG-PET for bladder cancer patients. It shows there is a strong benefit to PET/CT and that it can have a clinical impact on patient management.”