Prognostic Value of Quantitative Metabolic Metrics on Baseline Pre-Sunitinib FDG PET/CT in Advanced Renal Cell Carcinoma

Prognostic importance of SUVmax values evaluated by 18F-FDG-PET/CT before nivolumab treatment in patients with metastatic renal cell carcinoma

BACKGROUND

Nivolumab is a monoclonal antibody that binds to the programmed death-1 (PD-1) receptor and blocks its interaction with PD-L1 and PD-L2. High response rates have been achieved with its use in the treatment of metastatic renal cell carcinoma (mRCC). We aimed to determine a relationship between 18-Fluoro-2-Deoxy-D-Glucose Positron Emission Tomography/Computed Tomography (18F-FDG-PET/CT) performed before nivolumab treatment and treatment-related survival.

METHODS

Between 2014 and 2021, 32 patients who received nivolumab and had pre-treatment 18F-FDG-PET/CT evaluation were included in this retrospective study. The total SUVmax (sum of SUVmax) of all tumoral foci and the lesion with the highest SUVmax value were recorded. The relationship of these values with progression-free survival (PFS) and overall survival (OS) was evaluated.

RESULTS

The median highest SUVmax and sum of SUVmax values were found as 14.4 and 41.4, respectively. PFS and OS were longer in the group with a sum of SUVmax value below 41.4 compared to the group with a higher group (OS, median 9.52 vs. 4.2 months [P=0.018]; PFS, median 9.6 vs. 3 months [P=0.003], respectively). In the group with the highest SUVmax value below 14.4, PFS was evaluated as statistically significant compared to the higher group (PFS, median 16.74 vs. 3.3 months [P=0.004]), while OS was not found to be statistically significant (OS, median 25.45 vs. 16.74 months (P=0.110)).

CONCLUSIONS

Our study showed that there might be a relationship between SUVmax values and PFS and OS. The SUVmax values before nivolumab treatment can be used to predict prognosis and survival in mRCC patients.

Non-invasive molecular imaging of kidney diseases

In nephrology, differential diagnosis or assessment of disease activity largely relies on the analysis of glomerular filtration rate, urinary sediment, proteinuria and tissue obtained through invasive kidney biopsies. However, currently available non-invasive functional parameters, and most serum and urine biomarkers, cannot capture intrarenal molecular disease processes specifically. Moreover, although histopathological analyses of kidney biopsy samples enable the visualization of pathological morphological and molecular alterations, they only provide information about a small part of the kidney and do not allow longitudinal monitoring. These limitations not only hinder understanding of the dynamics of specific disease processes in the kidney, but also limit the targeting of treatments to active phases of disease and the development of novel targeted therapies. Molecular imaging enables non-invasive and quantitative assessment of physiological or pathological processes by combining imaging technologies with specific molecular probes. Here, we discuss current preclinical and clinical molecular imaging approaches in nephrology. Non-invasive visualization of the kidneys through molecular imaging can be used to detect and longitudinally monitor disease activity and can therefore provide companion diagnostics to guide clinical trials, as well as the safe and effective use of drugs.

CT and MRI compatibility of flexible 3D-printed materials for soft actuators and robots used in image-guided interventions

PURPOSE

Three-dimensional (3D) printing allows for the fabrication of medical devices with complex geometries, such as soft actuators and robots that can be used in image-guided interventions. This study investigates flexible and rigid 3D-printing materials in terms of their impact on multimodal medical imaging.

METHODS

The generation of artifacts in clinical computer tomography (CT) and magnetic resonance (MR) imaging was evaluated for six flexible and three rigid materials, each with a cubical and a cylindrical geometry, and for one exemplary flexible fluidic actuator. Additionally, CT Hounsfield units (HU) were quantified for various parameter sets iterating peak voltage, x-ray tube current, slice thickness, and convolution kernel.

RESULTS

We found the image artifacts caused by the materials to be negligible in both CT and MR images. The HU values mainly depended on the elemental composition of the materials and applied peak voltage was ranging between 80 and 140 kVp. Flexible, nonsilicone-based materials were ranged between 51 and 114 HU. The voltage dependency was less than 29 HU. Flexible, silicone-based materials were ranged between 60 and 365 HU. The voltage-dependent influence was as large as 172 HU. Rigid materials ranged between -69 and 132 HU. The voltage-dependent influence was <33 HU.

CONCLUSIONS

All tested materials may be employed for devices placed in the field of view during CT and MR imaging as no significant artifacts were measured. Moreover, the material selection in CT could be based on the desired visibility of the material depending on the application. Given the wide availability of the tested materials, we expect our results to have a positive impact on the development of devices and robots for image-guided interventions.

Comparison of Quantitative Methods on FDG PET/CT for Treatment Response Evaluation of Metastatic Colorectal Cancer

PURPOSE

FDG PET is effective in treatment response evaluation of cancer. However, there is no standard method for quantitative evaluation of FDG PET, particularly regarding cytostatic drugs. We compared various FDG PET quantitative methods in terms of response determination.

METHODS

A total of 39 refractory metastatic colorectal cancer patients who received a multikinase inhibitor treatment were included. Baseline and posttreatment FDG PET/CT scans were performed before and two cycles after treatment. Standardized uptake value (SUV) and total lesion glycolysis (TLG) values using various margin thresholds (30-70 % of maximum SUV with increment 10 %, twice mean SUV of blood pool, SUV 3.0, and SUV 4.0) were measured, with measurement target of the hottest lesion or a maximum of five hottest lesions. Treatment response by the PERCIST criteria was also determined. Predictive values of the PET indexes were evaluated in terms of the treatment response determined by the RECIST 1.1 criteria.

RESULTS

The agreement rate was 38 % between response determined by the PERCIST and the RECIST criteria (κ = 0.381). When patients were classified into disease control group (PR, SD) and non-control group (PD) by the RECIST criteria, percent changes of TLG with various margin thresholds (particularly, 30-50 % of maximum SUV) exhibited significant differences between the two groups, and high diagnostic power for the response by the RECIST criteria. TLG-based criteria, which used a margin threshold of 50 % of maximum SUV, exhibited a high agreement with the RECIST criteria compared with the PERCIST criteria (κ = 0.606).

CONCLUSION

In metastatic colorectal cancer, FDG PET/CT could be effective for treatment response evaluation by using TLG measured by margin thresholds of 30-50 % of maximum SUV. Further studies are warranted regarding the optimal cutoff values for this method.