Intratumoral heterogeneity after targeted therapy in murine cancer models with differing degrees of malignancy

INTRODUCTION

Conventional morphologic and volumetric assessment of treatment response is not suitable for adequately assessing responses to targeted cancer therapy. The aim of this study was to evaluate changes in tumor composition after targeted therapy in murine models of breast cancer with differing degrees of malignancy via non-invasive magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Mice bearing highly malignant 4T1 tumors or low malignant 67NR tumors were treated with either a combination of two immune checkpoint inhibitors (ICI, anti-PD1 and anti-CTLA-4) or the multi-tyrosine kinase inhibitor sorafenib, following experiments with macrophage-depleting clodronate-loaded liposomes and vessel-stabilizing angiopoietin-1. Mice were imaged on a 9.4 T small animal MRI system with a multiparametric (mp) protocol, comprising T1 and T2 mapping and diffusion-weighted imaging. Tumors were analyzed ex vivo with histology.

RESULTS AND DISCUSSIONS

All treatments led to an increase in non-viable areas, but therapy-induced intratumoral changes differed between the two tumor models and the different targeted treatments. While ICI treatment led to intratumoral hemorrhage, sorafenib treatment mainly induced intratumoral necrosis. Treated 4T1 tumors showed increasing and extensive areas of necrosis, in comparison to 67NR tumors with only small, but also increasing, necrotic areas. After either of the applied treatments, intratumoral heterogeneity, was increased in both tumor models, and confirmed ex vivo by histology. Apparent diffusion coefficient with subsequent histogram analysis proved to be the most sensitive MRI sequence. In conclusion, mp MRI enables to assess dedicated therapy-related intratumoral changes and may serve as a biomarker for treatment response assessment.

Perfusion Change of Hepatocellular Carcinoma During Atezolizumab plus Bevacizumab Treatment: A Pilot Study

PURPOSE

To investigate whether the early perfusion change in hepatocellular carcinoma (HCC) predicts the long-term therapeutic response to atezolizumab plus bevacizumab.

METHODS

We retrospectively selected 19 subjects (median age: 62 years, 4 females, and 15 males) having advanced HCC and treated with atezolizumab alone (n = 3) or in combination with bevacizumab (n = 16). The 4-phased CT or MRI imaging was performed for each subject before and at 9 ± 2 and 21 ± 5 weeks after therapy initiation. The tumor-to-liver signal ratio in the arterial phase was used to estimate the tumor perfusion. The change in tumor perfusion from the baseline to the 1st follow-up exam was correlated with the tumor response evaluated using mRECIST at the 2nd follow-up exam. The difference between favorably responding and non-responding groups was statistically analyzed using one-way ANOVA.

RESULTS

The mean tumor long axis in the baseline image was 59 ± 47 mm. The HCC perfusion changes were -26 ± 18% for complete (or partial) response (CR/PR, n = 8), -24 ± 12% for stable disease (SD, n = 8), and 9 ± 13% for progressive disease (PD, n = 3). The HCC perfusion change of the CR/PR groups was significantly lower than that of the PD group (p = 0.0040). The HCC perfusion changes between the SD and PD groups were also significantly different (p = 0.0135). The sensitivity and specificity of the early perfusion change to predict the long-term progression of the disease were 100 and 94%, respectively.

CONCLUSION

The early change in HCC perfusion may predict the long-term therapeutic response to atezolizumab plus bevacizumab, promoting personalized treatment for HCC patients.

FDG PET Hybrid Imaging

Molecular imaging with positron emission tomography (PET) using tumour-seeking radiopharmaceuticals has gained wide acceptance in oncology with many clinical applications. The hybrid imaging modality PET/CT (computed tomography) allows assessing molecular as well as morphologic information at the same time. Therefore, PET/CT represents an efficient tool for whole-body staging and re-staging within one imaging modality. In oncology, the glucose analogue 18-F-fluorodeoxyglucose (FDG) is the most widely used PET/CT radiopharmaceutical in clinical routine. FDG PET and FDG PET/CT have been used for staging and re-staging of tumour patients in numerous studies. This chapter will discuss the use and the main indications of FDG PET/CT in oncology with special emphasis on lung cancer, lymphoma, head and neck cancer, melanoma and breast cancer (among other tumour entities). A review of the current literature is given with respect to primary diagnosis, staging and diagnosis of recurrent disease. Besides its integral role in diagnosis, staging and re-staging of disease in oncology, there is increasing evidence that FDG PET/CT can be used for therapy response assessment (possibly influencing therapeutic management and treatment planning) by evaluating tumour control, which will also be discussed in this chapter.

Automated Definition of Skeletal Disease Burden in Metastatic Prostate Carcinoma: A 3D Analysis of SPECT/CT Images

To meet the current need for skeletal tumor-load estimation in castration-resistant prostate cancer (CRPC), we developed a novel approach based on adaptive bone segmentation. In this study, we compared the program output with existing estimates and with the radiological outcome. Seventy-six whole-body single-photon emission computed tomographies/x-ray computed tomography with 3,3-diphosphono-1,2-propanedicarboxylic acid from mCRPC patients were analyzed. The software identified the whole skeletal volume (S_Vol) and classified the voxels metastases (M_Vol) or normal bone (B_Vol). S_Vol was compared with the estimation of a commercial software. M_Vol was compared with manual assessment and with prostate specific antigen (PSA) levels. Counts/voxel were extracted from M_Vol and B_Vol. After six cycles of ²²³RaCl2-therapy every patient was re-evaluated as having progressive disease (PD), stable disease (SD), or a partial response (PR). S_Vol correlated with that of the commercial software (R = 0.99, p < 0.001). M_Vol correlated with the manually-counted lesions (R = 0.61, p < 0.001) and PSA (R = 0.46, p < 0.01). PD had a lower counts/voxel in M_Vol than PR/SD (715 ± 190 vs. 975 ± 215 and 1058 ± 255, p < 0.05 and p < 0.01) and B_Vol (PD 275 ± 60, PR 515 ± 188 and SD 528 ± 162 counts/voxel, p < 0.001). Segmentation-based tumor load correlated with radiological/laboratory indices. Uptake was linked with the clinical outcome, suggesting that metastases in PD patients have a lower affinity for bone-seeking radionuclides and might benefit less from bone-targeted radioisotope therapies.

Computer-aided volumetric assessment of malignant pleural mesothelioma on CT using a random walk-based method

OBJECTIVE

The aim of this study is to assess the performance of a computer-aided semi-automated algorithm we have adapted for the purpose of segmenting malignant pleural mesothelioma (MPM) on CT.

METHODS

Forty-five CT scans were collected from 15 patients (M:F [Formula: see text] 10:5, mean age 62.8 years) in a multi-centre clinical drug trial. A computer-aided random walk-based algorithm was applied to segment the tumour; the results were then compared to radiologist-drawn contours and correlated with measurements made using the MPM-adapted Response Evaluation Criteria in Solid Tumour (modified RECIST).

RESULTS

A mean accuracy (Sørensen-Dice index) of 0.825 (95% CI [0.758, 0.892]) was achieved. Compared to a median measurement time of 68.1 min (range [40.2, 102.4]) for manual delineation, the median running time of our algorithm was 23.1 min (range [10.9, 37.0]). A linear correlation (Pearson's correlation coefficient: 0.6392, [Formula: see text]) was established between the changes in modified RECIST and computed tumour volume.

CONCLUSION

Volumetric tumour segmentation offers a potential solution to the challenges in quantifying MPM. Computer-assisted methods such as the one presented in this study facilitate this in an accurate and time-efficient manner and provide additional morphological information about the tumour's evolution over time.

Prospective evaluation of [11C]Choline PET/CT in therapy response assessment of standardized docetaxel first-line chemotherapy in patients with advanced castration refractory prostate cancer

PURPOSE

The aim of this study was to prospectively evaluate the value of [¹¹C] Choline PET/CT in monitoring early and late response to a standardized first-line docetaxel chemotherapy in castration refractory prostate cancer (mCRPC) patients.

METHODS

Thirty-two patients were referred for [¹¹C] Choline PET/CT before the start of docetaxel chemotherapy, after one and ten chemotherapy cycles (or - in case of discontinuation - after the last administered cycle) for therapy response assessment. [¹¹C] Choline uptake (SUV_max, SUV_mean), CT derived Houndsfield units (HU_max, HU_mean), and volume of bone, lung, and nodal metastases and local recurrence were measured semi-automatically at these timepoints. Change in SUV_max, SUV_mean, HU_max, HU_mean, and volume was assessed between PET 2 and 1 (early response assessment, ERA) and PET 3 and 1 (late response assessment, LRA) on a patient and lesion basis. Results of PET/CT were compared to clinically used RECIST 1.1 and clinical criteria based therapy response assessment including PSA for defining progressive disease (PD) and non-progressive disease (nPD), respectively. Relationships between changes of SUV_max and SUV_mean (early and late) and changes of PSA_early and PSA_late were evaluated. Prognostic value of initial SUV_max and SUV_mean was assessed. Statistical analyses were performed using SPSS.

RESULTS

In the patient-based ERA and LRA there were no statistically significant differences in change of choline uptake, HU, and volume between PD and nPD applying RECIST or clinical response criteria. In the lesion-based ERA, decrease in choline uptake of bone metastases was even higher in PD (applying RECIST criteria), whereas in LRA the decrease was higher in nPD (applying clinical criteria). There were only significant correlations between change in choline uptake and PSA in ERA in PD, in LRA no significant correlations were discovered. Initial SUV_max and SUV_mean were statistically significantly higher in nPD (applying clinical criteria).

CONCLUSION

There is no significant correlation between change in choline uptake in [¹¹C] Choline PET/CT and clinically routinely used objective response assessment during the early and late course of docetaxel chemotherapy. Therefore, [¹¹C] Choline PET/CT seems to be of limited use in therapy response assessment in standardized first-line chemotherapy in mCRPC patients.

Comparison of NaF and FDG PET/CT for assessment of treatment response in castration-resistant prostate cancers with osseous metastases

BACKGROUND

Assessment of skeletal metastases' response to therapy is a highly relevant but unresolved clinical problem. The main goal of this work was to compare pharmacodynamic responses to therapy assessed with positron emission tomography-computed tomography (PET/CT) using fluorine-18 sodium fluoride (NaF) and fluorine-18 fluorodeoxyglucose (FDG) as the tracers.

MATERIALS AND METHODS

Patients with prostate cancer with known osseous metastases were treated with zibotentan (ZD4054) and imaged with combined dynamic NaF/FDG PET/CT before therapy (baseline), after 4 weeks of therapy (week 4), and after 2 weeks of treatment break (week 6). Kinetic analysis allowed comparison of the voxel-based tracer uptake rate parameter Ki, the vasculature parameters K1 (measuring perfusion/permeability) and Vb (measuring vasculature fraction in the tissue), and the standardized uptake values (SUVs).

RESULTS

Correlations were high for the NaF and FDG peak uptake parameters (Ki and SUV correlations ranged from 0.57 to 0.88) and for vasculature parameters (K1 and Vb correlations ranged from 0.61 to 0.81). Correlation was low between the NaF and FDG week 4 Ki responses (ρ = 0.35; P = .084) but was higher for NaF and FDG week 6 Ki responses (ρ = 0.72; P < .0001). Correlations for vasculature responses were always low (ρ < 0.35). NaF and FDG uptakes in the osseous metastases were spatially dislocated, with overlap in the range from 0% to 80%.

CONCLUSION

This study found that late NaF and FDG uptake responses are consistently correlated but that earlier uptake responses and all vasculature responses can be unrelated. This study also confirmed that FDG and NaF uptakes are spatially dislocated. Although treatment responses assessed with NaF and FDG may be correlated, using both tracers provides additional information.