A convolutional neural network for fully automated blood SUV determination to facilitate SUR computation in oncological FDG-PET

Asphericity derived from [18F]FDG PET as a new prognostic parameter in cervical cancer patients

The objective of this study was to assess the prognostic value of asphericity (ASP) and standardized uptake ratio (SUR) in cervical cancer patients. Retrospective analysis was performed on a group of 508 (aged 55 ± 12 years) previously untreated cervical cancer patients. All patients underwent a pretreatment [¹⁸F]FDG PET/CT study to assess the severity of the disease. The metabolic tumor volume (MTV) of the cervical cancer was delineated with an adaptive threshold method. For the resulting ROIs the maximum standardized uptake value (SUV_max) was measured. In addition, ASP and SUR were determined as previously described. Univariate Cox regression and Kaplan-Meier analysis with respect to event free survival (EFS), overall survival (OS), freedom from distant metastasis (FFDM) and locoregional control (LRC) was performed. Additionally, a multivariate Cox regression including clinically relevant parameters was performed. In the survival analysis, MTV and ASP were shown to be prognostic factors for all investigated endpoints. Tumor metabolism quantified with the SUV_max was not prognostic for any of the endpoints (p > 0.2). The SUR did not reach statistical significance either (p = 0.1, 0.25, 0.066, 0.053, respectively). In the multivariate analysis, the ASP remained a significant factor for EFS and LRC, while MTV was a significant factor for FFDM, indicating their independent prognostic value for the respective endpoints. The alternative parameter ASP has the potential to improve the prognostic value of [¹⁸F]FDG PET/CT for event-free survival and locoregional control in radically treated cervical cancer patients.

64Cu-/177Lu-Cetuximab Theranostic Pair: May the Single 64Cu-Cetuximab Diagnostic Scan Be Acquired at Any Time After Injection?

Two independent equations were recently proposed for estimating ¹⁷⁷Lu-cetuximab cumulative activity, in a preclinical situation, from an initial ⁶⁴Cu-cetuximab diagnostic scan acquired at peak time of decay-uncorrected (t_peak-uncorr) or decay-corrected (t_peak-corr) time-activity curve of trapped ⁶⁴Cu-cetuximab, respectively. The standard uptake ratio (SUR) measured at t_peak-uncorr or t_peak-corr turned out to be a key metric in each equation, respectively. However, acquiring the diagnostic scan at t_peak-uncorr or t_peak-corr might be a limitation of the proposed method. Therefore, in an attempt to overcome this limitation, this note aims at theoretically investigating whether SUR(t_peak-uncorr) and/or SUR(t_peak-corr) could be derived from a diagnostic scan acquired at any time postinjection.

PET/CT for Predicting Occult Lymph Node Metastasis in Gastric Cancer

A portion of gastric cancer patients with negative lymph node metastasis at an early stage eventually die from tumor recurrence or advanced metastasis. Occult lymph node metastasis (OLNM] is a potential risk factor for the recurrence and metastasis in these patients, and it is highly important for clinical prognosis. Positron emission tomography (PET)/computed tomography (CT) is used to assess lymph node metastasis in gastric cancer due to its advantages in anatomical and functional imaging and non-invasive nature. Among the major metabolic parameters of PET, the maximum standardized uptake value (SUVmax) is commonly used for examining lymph node status. However, SUVmax is susceptible to interference by a variety of factors. In recent years, the exploration of new PET metabolic parameters, new PET imaging agents and radiomics, has become an active research topic. This paper aims to explore the feasibility and predict the effectiveness of using PET/CT to detect OLNM. The current landscape and future trends of primary metabolic parameters and new imaging agents of PET are reviewed. For gastric cancer patients, the possibility to detect OLNM non-invasively will help guide surgeons to choose the appropriate lymph node dissection area, thereby reducing unnecessary dissections and providing more reasonable, personalized and comprehensive treatments.

Can Dynamic Whole-Body FDG PET Imaging Differentiate between Malignant and Inflammatory Lesions?

Background: Investigation of the clinical feasibility of dynamic whole-body (WB) [18F]FDG PET, including standardized uptake value (SUV), rate of irreversible uptake (Ki), and apparent distribution volume (Vd) in physiologic tissues, and comparison between inflammatory/infectious and cancer lesions. Methods: Twenty-four patients were prospectively included to undergo dynamic WB [18F]FDG PET/CT for clinically indicated re-/staging of oncological diseases. Parametric maps of Ki and Vd were generated using Patlak analysis alongside SUV images. Maximum parameter values (SUVmax, Kimax, and Vdmax) were measured in liver parenchyma and in malignant or inflammatory/infectious lesions. Lesion-to-background ratios (LBRs) were calculated by dividing the measurements by their respective mean in the liver tissue. Results: Seventy-seven clinical target lesions were identified, 60 malignant and 17 inflammatory/infectious. Kimax was significantly higher in cancer than in inflammatory/infections lesions (3.0 vs. 2.0, p = 0.002) while LBRs of SUVmax, Kimax, and Vdmax did not differ significantly between the etiologies: LBR (SUVmax) 3.3 vs. 2.9, p = 0.06; LBR (Kimax) 5.0 vs. 4.4, p = 0.05, LBR (Vdmax) 1.1 vs. 1.0, p = 0.18). LBR of inflammatory/infectious and cancer lesions was higher in Kimax than in SUVmax (4.5 vs. 3.2, p < 0.001). LBRs of Kimax and SUVmax showed a strong correlation (Spearman’s rho = 0.83, p < 0.001). Conclusions: Dynamic WB [18F]FDG PET/CT is feasible in a clinical setting. LBRs of Kimax were higher than SUVmax. Kimax was higher in malignant than in inflammatory/infectious lesions but demonstrated a large overlap between the etiologies.

Estimation of Cumulative Activity of 177Lu-Cetuximab from a Single Diagnostic 64Cu-Cetuximab Scan

Background: This study aimed at investigating whether a single diagnostic ⁶⁴Cu-cetuximab scan might predict therapeutic ¹⁷⁷Lu-cetuximab cumulative activity in a preclinical study. Methods: The framework of the reversible Patlak-Blasberg analysis was used to derive two independent equations of ¹⁷⁷Lu-cetuximab cumulative activity that involve the tumor-to-blood standard uptake value ratio (i.e., the SUR) assessed at peak-time of either decay-uncorrected or decay-corrected activity concentration of trapped ⁶⁴Cu-cetuximab, respectively. Applied to published data in TE-8 tumor-bearing mice, the two peak times and corresponding SUR values were assessed. Two estimates of ¹⁷⁷Lu-cetuximab cumulative activity were then computed for comparison with two previously published values obtained from different methods. Results: The two estimates of ¹⁷⁷Lu-cetuximab cumulative activity, computed at 14 and 59 h postinjection, were consistent with the previously published values: 4.7 × 10¹² and 5.5 × 10¹² versus 4.1 × 10¹² and 5.3 × 10¹² disintegrations/g. Conclusion: Two independent equations are proposed for estimating ¹⁷⁷Lu-cetuximab cumulative activity from an initial diagnostic ⁶⁴Cu-cetuximab scan, when acquired at two relevant injection acquisition times, respectively. Applied to published tumor-bearing mouse data, the ⁶⁴Cu-cetuximab SUR assessed at either 14 or 59 h postinjection turns out to be key metrics.

An abbreviated therapy-dosimetric equation for the companion diagnostic/therapeutic [64/67Cu]Cu-SARTATE

In a preclinical model of neuroblastoma, Dearling et al. recently demonstrated the potential interest for a theranostic approach of [⁶⁴/⁶⁷Cu]Cu-SARTATE for the detection and treatment of SSTR2-positive neuroblastoma lesions in pediatric patients whose widespread metastases survive initial therapy as minimal residual disease (MRD). MRD may be detected by [⁶⁴Cu]Cu-SARTATE and subsequently treated by [⁶⁷Cu]Cu-SARTATE. Since therapeutic dosimetry estimation of the latter agent from the uptake of the former one in the initial diagnostic scan was not addressed, the present theoretical commentary proposes the derivation of an abbreviated therapy-dosimetric equation for the companion diagnostic/therapeutic [⁶⁴/⁶⁷Cu]Cu-SARTATE that might be of interest for future clinical theranostic practice.