Histological Validation of 11Carbon-Acetate Positron Emission Tomography/Computerized Tomography in Detecting Lymph Node Metastases in Prostate Cancer.

PURPOSE: Conventional imaging cannot definitively detect nodal metastases of prostate cancer. We histologically validated C-acetate positron emission tomography/computerized tomography to identify nodal metastases, examining prostate cancer factors that influence detection rates.

MATERIALS AND METHODS: Patients with C-acetate avid positron emission tomography/computerized tomography imaged pelvic/retroperitoneal lymph nodes underwent high extended robotic lymphadenectomy. A standardized mapping template comprising 8 predetermined anatomical regions was dissected during lymphadenectomy, allowing for matched, region based analysis and comparison of imaging and histological data.

RESULTS: In 25 patients a total of 2,149 lymph nodes were excised (mean 86 per patient, range 27 to 136) and 528 (22%) harbored metastases (mean 21 positive nodes per patient, range 0 to 109). A total of 174 anatomical regions had matching imaging histological data. C-acetate positron emission tomography/computerized tomography accurately identified 48 node-positive regions and accurately ruled out 88 regions as metastasis-free. C-acetate sensitivity, specificity, and positive and negative predictive values were 67%, 84%, 74% and 79%, respectively. An increasing, histologically measured metastatic lesion size in long axis diameter of 5 or less, 6 to 10, 11 to 15, 16 to 20 and 21 mm or greater correlated with improved C-acetate detection rates of 45%, 62%, 81%, 89% and 100%, respectively. Each standard uptake value unit increase correlated with a 1.9 mm increase in nodal long axis diameter (p <0.001) and a 1.2 mm increase in short axis diameter (p <0.001). Positive C-acetate positron emission tomography/computerized tomography findings correlated with histological lymph node size (long axis diameter 12 mm and short axis diameter 6 mm), metastatic lesion size (long axis diameter 11 mm and short axis diameter 6 mm) and extranodal extension (positive 88% vs false-negative 58%, p = 0.005).

CONCLUSIONS: C-acetate positron emission tomography/computerized tomography can identify prostate cancer metastatic nodal disease. However, it underestimates the true cephalad extent of nodal involvement, performing better in the pelvis than in the retroperitoneum. Standard uptake value, histological nodal size, intranodal metastasis size and extranodal extension correlate with cancer bearing nodes.