Molecular Imaging for Evaluation of Viable Testicular Cancer Nodal Metastases

Determining the metastatic viability of suspicious retroperitoneal nodes in testicular cancer with conventional imaging is challenging. The aim of this report is to review recent evidence in the utilization of novel imaging modalities to assess viable testicular cancer nodal metastases.

Testicular germ cell tumors (TCGTs) follow a predictable lymphatic metastatic spread to the retroperitoneum. Accordingly, retroperitoneal imaging is critical in staging, assessing treatment response, and evaluating for recurrence. Conventional computed tomography (CT) imaging is effective in diagnosing pathologically enlarged lymph nodes but lacks the molecular information to determine if suspicious nodes harbor viable tumor. Positron emission tomography (PET) with the metabolic radiotracer 2-deoxy-2-[¹⁸F]fluoro-D-glucose (¹⁸F-FDG or FDG) has been shown to be useful in determining the presence of or absence of viable tumor after chemotherapy for seminoma, but its role with non-seminomatous germ cell tumors (NSGCTs) and other clinical scenarios is limited. Patients with residual masses after chemotherapy for NSGCT present a difficult challenge because surgical resection carries a high degree of morbidity despite many patients only harboring fibrosis on final pathology. Current imaging modalities are unable to effectively differentiate fibrosis from viable tumor on preoperative imaging. Novel molecular imaging techniques present promising opportunities to improve diagnosis in these patients. Novel imaging platforms have potential to improve the ability to determine viable nodal metastases regardless of size and structure but confirmatory studies are currently lacking.