Lay Summary: PET is not recommended by NCCN for non-seminomatous testicular carcinoma.
Most of the research on PET in testicular cancer focused on restaging, because functional assessment of residual masses after chemotherapy is of great clinical interest. Staging is less well studied. In a 2003, CMS reviewed 11 studies of FDG-PET in testicular cancer and concluded that the literature suggests a possible role for FDG PET in staging testicular cancer, but that studies had significant limitations and that further research was needed to confirm this finding. PET in general is covered for the listed indications if the results of the PET exam could potentially impact clinical management. Medicare requires the ordering physician to document in the patient medical record the indication and justification for ordering a PET study, including a statement of how the PET findings might impact clinical management. There are several difficulties with using FDG PET for distinguishing NCCN does not recommend PET for either seminomatous or non-seminomatous testicular cancer.
There are several difficulties with using FDG PET for distinguishing recurrence and residual disease from benign masses. FDG PET was not useful in detecting tumor of less than 0.5cm or teratoma of any size secondary to a low proliferation rate and glucose metabolism. Furthermore, FDG PET cannot reliably distinguish between teratoma and necrosis. Since FDG PET cannot reliably distinguish between teratoma, cancer and necrosis, regardless of a positive FDG PET, you will still resect the testicular mass (or at least perform a retroperitoneal lymph node dissection post chemotherapy if serum tumor markers are not elevated) because the standard of care is to leave no mass (or suspected recurrence) unexamined for fear of malignant transformation or “growing teratoma syndrome.” Though many studies showed FDG PET with a high specificity for detecting residual tumor, the converse, that sensitivity is low, is also true. Given this relationship, a negative FDG PET scan does not provide complete assurance that the patient does not have a mass requiring resection, especially in patients with NSGCT. To improve sensitivity of FDG PET, some authors advocate avoiding its use in patients with high probability of having residual teratoma (i.e. patients with teratomatous elements in the primary tumor). Notwithstanding the reportedly high specificity of FDG PET for detecting residual tumor, authors note that false positive results secondary to FDG PET accumulating in tissue macrophages are a common problem, especially post chemotherapy or if the patient has an infection. Additionally, false negative results are common post chemotherapy because the chemotherapy drug leads to a transient suppression of metabolic activity in germ cell tumors regardless of their final response to therapy. Though some authors conclude that they cannot recommend the routine use of FDG PET scans in the evaluation of residual postchemotherapy masses in seminoma, one potential safeguard against the false negative results is to perform PET scans at least 2 weeks or more after chemotherapy. A recent guideline rated this modality as 4 on a 4/10 scale for staging testicular cancer. However NCCN now recommends this modality, with sureillance for negative results and biopsy or surgery, if positive, for seminoma but not for non-seminoma. nccn.org, testicular, p. 6, 2009
Technology Assessment submitted to AHRQ by the Duke Center for Clinical Health Policy Research and Evidence Practice Center, David B. Matchar, MD, Shalini L. Kulasingam, PhD, Laura Havrilesky, MD, et al., December 2003.
Choyke PL, Bluth EI, Bush WH Jr, Casalino DD, Francis IR, Jafri SZ, Kawashima A, Papanicolaou N, Rosenfield AT, Sandler CM, Segal AJ, Tempany C, Resnick MI, Expert Panel on Urologic Imaging. Staging of testicular malignancy. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. 6 p. [57 references]