SUVs Are Adequate Measures of Lesional 18F-DCFPyL Uptake in Patients with Low Prostate Cancer Disease Burden

In prostate cancer (PCa) patients, the tumor-to-blood ratio (TBR) has been validated as the preferred simplified method for lesional ¹⁸F-DCFPyL (a radiolabeled prostate-specific membrane antigen ligand) uptake quantification on PET. In contrast to SUVs, the TBR accounts for variability in arterial input functions caused by differences in total tumor burden between patients (the sink effect). However, TBR depends strongly on tracer uptake interval and has worse repeatability and is less applicable in clinical practice than SUVs. We investigated whether SUV could provide adequate quantification of ¹⁸F-DCFPyL uptake on PET/CT in a patient cohort with low PCa burden. Methods: In total, 116 patients with PCa undergoing ¹⁸F-DCFPyL PET/CT imaging were retrospectively included. All ¹⁸F-DCFPyL-avid lesions suspected of being PCa were semiautomatically delineated. SUV_peak was plotted against TBR for the most intense lesion of each patient. The correlation of SUV_peak and TBR was evaluated using linear regression and was stratified for patients undergoing PET/CT for primary staging, patients undergoing restaging at biochemical recurrence, and patients with metastatic castration-resistant PCa. Moreover, the correlation was evaluated as a function of tracer uptake time, prostate-specific antigen level, and PET-positive tumor volume. Results: In total, 436 lesions were delineated (median, 1 per patient; range, 1-66). SUV_peak correlated well with TBR in patients with PCa and a total tumor volume of less than 200 cm³ (R ² = 0.931). The correlation between SUV and TBR was not affected by disease setting, prostate-specific antigen level, or tumor volume. SUV_peak depended less on tracer uptake time than did TBR. Conclusion: For ¹⁸F-DCFPyL PET/CT, SUV_peak correlates strongly with TBR. Therefore, it is a valuable simplified, semiquantitative measurement in patients with low-volume PCa (<200 cm³). SUV_peak can therefore be applied in ¹⁸F-DCFPyL PET assessment as an imaging biomarker to characterize tumors and to monitor treatment outcomes.

Improving the Prognostic Performance of SUVmax in 18F-Fluorodeoxyglucose Positron-Emission Tomography/Computed Tomography Using Tumor-to-Liver and Tumor-to-Blood Standard Uptake Ratio for Locally Advanced Cervical Cancer Treated with Concurrent Chemoradiotherapy

OBJECTIVE

We sought to evaluate whether the ¹⁸F-fluorodeoxyglucose uptake normalization of the primary tumor to both the liver and blood pool and lymph nodes to both the liver and blood pool can enhance the discrimination for prognosis prediction in patients with cervical cancer.

METHODS

A total of 156 patients with cervical cancer (International Federation of Gynecology and Obstetrics stages IIB-IV) treated with concurrent chemoradiotherapy (CCRT) were enrolled. The maximum standardized uptake value (SUV_max) of tumor (tSUV_max) and the lymph node (nSUV_max) divided by the SUV_mean of the liver (tumor-to-liver ratio (TLR) and node-to-liver (NLR)) and blood pool (tumor-to-blood ratio (TBR) and node-to-blood ratio (NBR)) were investigated. Univariate and multivariate analyses of disease-free survival (DFS) and overall survival (OS) were performed using clinical and metabolic parameters. A receiver operating characteristic curve analysis was performed to compare the accuracy of the metabolic parameters.

RESULTS

The multivariate analysis revealed that NLR (hazard ratio ((HR): 3.54; 95% confidence interval (CI): 1.53-8.19; p = 0.0032) and NBR (HR: 3.38; 95% CI: 1.02-11.19; p = 0.0457)) were independent prognostic factors for DFS, while TLR (HR: 4.16; 95% CI: 1.19-14.50; p = 0.0252), TBR (HR: 3.01; 95% CI: 1.04-8.70; p = 0.0415), NLR (HR: 4.84; 95% CI: 1.58-14.81; p = 0.0057), and NBR (HR: 6.87; 95% CI: 1.55-30.54; p = 0.0113) were significant prognostic factors for OS. The normalization of tSUV_max to the liver or blood pool enhanced the discrimination for prediction of recurrence (tSUV_max vs. TLR; p = 0.0056 and tSUV_max vs. TBR; p = 0.0099) and death (tSUV_max vs. TLR; p < 0.0001 and tSUV_max vs. TBR; p = 0.0001).

CONCLUSIONS

The normalization of tSUV_max was an independent prognostic factor and improved the discrimination for the prediction of tumor recurrence and death in patients with locally advanced cervical cancer treated with CCRT.