Imaging Response of Antiangiogenic and Immune-Oncology Drugs in Metastatic Renal Cell Carcinoma (mRCC): Current Status and Future Challenges

Prognostic Utility of Parameters Derived From Pretreatment Dual-Layer Spectral-Detector CT in Patients With Metastatic Renal Cell Carcinoma

Background: New therapies have emerged for metastatic renal cell carcinoma (mRCC), though corresponding imaging markers are lacking. Dual-layer spectral-detector CT (DLCT) can quantify iodine concentration (IC) and effective atomic number (Zeffective), providing information beyond attenuation that may indicate mRCC prognosis. Objective: To assess the utility of the DLCT-derived parameters IC and Zeffective for predicting mRCC treatment response and survival. Methods: This prospective study (ClinicalTrials.gov identifier: NCT03616951) enrolled 120 participants with mRCC from January 2018 to January 2020 who underwent DLCT before treatment initiation, with reconstruction of IC and Zeffective maps. Final analysis included 115 participants (86 men, 29 women; median age, 65.1 years), incorporating 313 target lesions that were clinically selected using RECIST version 1.1 on arterial-phase acquisitions of the chest and abdomen. Semiautomatic volumetric segmentation was performed of the target lesions. Pixels from all lesions were combined to a single histogram per patient. Median IC and Zeffective of the combined histograms were recorded. Measurements above and below the cohort median values were considered high and low, respectively. Univariable associations were explored between IC and Zeffective, with objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). Multivariable associations were explored between IC and ORR, PFS, and OS, adjusting for treatment (tyrosine kinase inhibitor versus checkpoint immunotherapy) and significant univariable predictors [including tumor histology and International mRCC Database Consortium (IMDC) risk factors]. Results: At baseline, median IC was 2.26 mg/ml, and median Zeffective was 8.49. In univariable analysis, high IC and high Zeffective were associated with better ORR (both OR=4.35, p=.001), better PFS (both HR=0.51, p=.004), and better OS (both HR=0.38, p<.001). In multivariable models, high IC independently predicted better ORR (OR=4.35, p=.001), better PFS (HR=0.51, p=.004), and better OS (HR=0.37, p<.001); neutrophilia independently predicted worse PFS (HR=2.10, p=.004) and worse OS (HR=2.28, p=.003). The estimated c-index for predicting OS using IMDC risk factors was 0.650, versus 0.687 when incorporating high attention and 0.692 when incorporating high IC or high Zeffective. Conclusions: High IC and high Zeffective are significant predictors of better treatment response and survival in mRCC. Clinical impact: Baseline DLCT parameters may improve current mRCC prognostic models.

Blood Volume as a new functional image-based biomarker of progression in metastatic renal cell carcinoma

RECIST v1.1 has limitations in evaluating progression. We assessed Dynamic Constrast Enhanced Computed Tomography (DCE-CT) identified Blood Volume (BV) for the evaluation of progressive disease (PD) in patients with metastatic renal cell carcinoma (mRCC). BV was quantified prospectively at baseline, after one month, then every three months until PD. Relative changes (ΔBV) were assessed at each timepoint compared with baseline values. The primary endpoint was Time to PD (TTP), the secondary endpoint was Time to the scan prior to PD (PDminus1). Cox proportional hazard models adjusted ΔBV for treatments and International mRCC Database Consortium factors. A total of 62 patients had analyzable scans at the PD timepoint. Median BV was 23.92 mL × 100 g^-1 (range 4.40-399.04) at PD and 26.39 mL × 100 g^-1 (range 8.70-77.44) at PDminus1. In the final multivariate analysis higher ΔBV was statistically significantly associated with shorter Time to PD, HR 1.11 (95% CI 1.07-1.15, P < 0.001). Also assessed at PDminus1, higher ΔBV was significantly associated with shorter time to PD, HR 1.14 (95% CI 1.01-1.28, P = 0.031). In conclusion, DCE-CT identified BV is a new image-based biomarker of therapy progression in patients with mRCC.

Feasibility Study on Using Dynamic Contrast Enhanced MRI to Assess the Effect of Tyrosine Kinase Inhibitor Therapy within the STAR Trial of Metastatic Renal Cell Cancer

Objective: To identify dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters predictive of early disease progression in patients with metastatic renal cell cancer (mRCC) treated with anti-angiogenic tyrosine kinase inhibitors (TKI). Methods: The study was linked to a phase II/III randomised control trial. Patients underwent DCE-MRI before, at 4- and 10-weeks after initiation of TKI. DCE-MRI parameters at each time-point were derived from a single-compartment tracer kinetic model, following semi-automated tumour segmentation by two independent readers. Primary endpoint was correlation of DCE-MRI parameters with disease progression at 6-months. Receiver operating characteristic (ROC) curve analysis and area under the curve (AUC) values were calculated for parameters associated with disease progression at 6 months. Inter-observer agreement was assessed using the intraclass correlation coefficient (ICC). Results: 23 tumours in 14 patients were measurable. Three patients had disease progression at 6 months. The percentage (%) change in perfused tumour volume between baseline and 4-week DCE-MRI (p = 0.016), mean transfer constant K^trans change (p = 0.038), and % change in extracellular volume (p = 0.009) between 4- and 10-week MRI, correlated with early disease progression (AUC 0.879 for each parameter). Inter-observer agreement was excellent for perfused tumour volume, K^trans and extracellular volume (ICC: 0.928, 0.949, 0.910 respectively). Conclusions: Early measurement of DCE-MRI biomarkers of tumour perfusion at 4- and 10-weeks predicts disease progression at 6-months following TKI therapy in mRCC.

Tumor response criteria for assessing pazopanib first-line therapy in patients with metastatic renal cell carcinoma (mRCC)

PURPOSE

To identify the optimum response criteria for first-line targeted pazopanib therapy in patients with mRCC using solid tumor response criteria and clinical risk factors.

METHODS

Pre- and post-treatment CTs of patients (n = 43) with mRCC treated with first-line pazopanib therapy were analyzed retrospectively. Treatment response was evaluated with Response Evaluation Criteria in Solid Tumors (RECIST) v1.1, Choi, modified Choi (mChoi), revised Choi (rChoi), MASS (Morphology, Attenuation, Size, and Structure), 10% threshold criteria, and subjective assessment. Memorial Sloan-Kettering Cancer Center and International Metastatic Renal Cell Carcinoma Database Consortium clinical risk factors were also used to define response groups. Response evaluations were correlated with overall survival (OS) and progression-free survival (PFS) using log-rank test.

RESULTS

Patients with partial response (PR) by mChoi and rChoi had longer OS than those with stable disease (SD) (P < 0.001). Responders by 10% threshold criteria also had better OS, without or combined with clinical criteria. Patients with PR by rChoi, mChoi, RECIST v1.1, MASS criteria, and by subjective assessment had longer PFS than those with SD. rChoi and mChoi criteria best delineated the difference in PFS for patients with PR versus SD, without or combined with clinical criteria.

CONCLUSION

For mRCC patients treated with pazopanib, OS and PFS for PR and SD groups were best predicted by rChoi and mChoi criteria, without or combined with clinical risk factors. 10% threshold criteria also predicted OS and PFS, whereas RECIST did so only in a limited number of patients.