Oncologic Angiogenesis Imaging in the clinic---how and why

Combined prognostic value of the SUVmax derived from FDG-PET and the lymphocyte-monocyte ratio in patients with stage IIIB-IV non-small cell lung cancer receiving chemotherapy

Background

We evaluated the prognostic potential of tumor ¹⁸F-fluorodeoxyglucose (FDG) uptake derived from positron emission tomography (PET) and known inflammatory hematological markers, both individually and in combination, for chemosensitivity and survival in patients with stage IIIB-IV non-small cell lung cancer (NSCLC) receiving first-line chemotherapy.

Methods

A total of 149 patients with stage IIIB and IV NSCLC (based on TNM 7th edition) were retrospectively reviewed. Maximum standardized uptake value (SUVmax) were used to quantitatively assess FDG uptake. The lymphocyte-monocyte ratio (LMR), neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) were selected as hematological markers. Receiver operating characteristic (ROC) curves were constructed for the determination of optimal cut-off values to predict chemotherapeutic response.

Results

Patients with SUVmax > 11.6 or LMR ≤3.73 exhibited a significantly lower objective response rate (ORR) to chemotherapy (p < 0.001 and p < 0.001). Through multivariable logistic regression analysis, both the SUVmax and LMR were identified as independent predictive factors for chemotherapeutic response (p = 0.001 and p < 0.001). Furthermore, a multivariable Cox proportional hazard model identified a high SUVmax (> 11.6) and low LMR (≤3.73) as independent predictors of poor PFS (p < 0.001 and p = 0.025) and OS (p < 0.001 and p = 0.032). A novel score system was constructed based on the SUVmax and LMR (SUV_LMR score), and patients were stratified into three subgroups. The patients with a score of 0 had a significantly higher ORR (88.9%) than did those with a score of 1 (59.6%) and score of 2 (25.0%) (p < 0.001). Moreover, multivariable Cox analysis further identified the SUV_LMR score as an independent prognostic factor for PFS (p < 0.001) and OS (p < 0.001).

Conclusions

Pre-treatment SUVmax and LMR were not only predictive factors for chemotherapeutic response but also independent prognostic factors of survival in stage IIIB-IV NSCLC. Moreover, the SUV_LMR score, which is based on primary tumor metabolic activity and the systemic inflammatory response, might provide a promising tool to predict chemosensitivity, recurrence and survival of advanced NSCLC.

The Distribution Volume of 18F-Albumin as a Potential Biomarker of Antiangiogenic Treatment Efficacy

Objective: 18F-albumin, a vascular imaging agent, may have potential to assess tumor responses to anti-angiogenic therapies. In these studies tumor distribution volume of 18F-albumin were first determined in various human tumor xenografts from biodistribtuion measurments and then one of the tumor type was used to evaluate changes in 18F-albumin uptake in anti-angiognic tumor model. Method: 18F-albumin was synthesized via conjugation of 6-[18F]fluoronicotinic acid-2,3,5,6-tetrafluorophenyl ester, [18F]F-Py-TFP, with rat albumin. From the biodistribution of 18F-albumin in various human tumor xenografts tumor distribution volumes (DVs; tumor%ID/g:blood%ID/g) were first determined at various time points. Then, the ability of 18F-albumin to detect tumor angiogenic inhibition in one of these tumor types (U87MG) following treatment with sunitinib was evaluated by position emission tomography (PET) imaging at 0, 7, 14, and 21 days post treatment. Caliper measurements of tumor dimensions were also made at these same times. At Day 21, following imaging, biodistributions, autoradiography of tumor tissues and tumor blood vessel counts (CD31 IHC) were performed. Results: 18F-albumin retention in various tumors steadily increased over time with U87MG tumor exhibiting the highest uptake (DV) at all times. Significant decreases in 18F-albumin DVs were observed one week post-treatement (-39%) vs. controls whereas tumor caliper volumes were not significantly decreased until days 14 and 21. At day 21 the significant decrease in DVs in the treatment group (-44%) paralleled biodistribution DV measurements and was consistent with autoradiography and CD31 IHC findings. Conclusion: These data suggest that 18F-albumin DVs obtained by imaging may serve as an early biomarker of the effectiveness of anti-angiogenic therapy and thus aid in patient management and treatment planning.

Functional evaluation of therapeutic response of HCC827 lung cancer to bevacizumab and erlotinib targeted therapy using dynamic contrast-enhanced and diffusion-weighted MRI

This study aimed to investigate the therapeutic responses of lung cancer mice models with adenocarcinoma HCC827 (gefitinib sensitive) and HCC827R (gefitinib resistant) to the epidermal growth factor receptor-tyrosine kinase inhibitor erlotinib alone and in combination with the anti-angiogenesis agent bevacizumab using dynamic contrast enhanced (DCE) and diffusion-weighted MRI. In the HCC827 model, temporal changes in DCE-MRI derived parameters (K^trans, k_ep, and iAUC₉₀) and apparent diffusion coefficient (ADC) were significantly correlated with tumor size. K^trans and iAUC₉₀ significantly decreased at week 2 in the groups receiving erlotinib alone and in combination with bevacizumab, whereas k_ep decreased at week 1 and 2 in both treatment groups. In addition, there was a significant difference in iAUC₉₀ between the treatment groups at week 1. Compared to the control group of HCC827, there was a significant reduction in microvessel density and increased tumor apoptosis in the two treatment group. ADC value increased in the erlotinib alone group at week 1 and week 2, and in the erlotinib combined with bevacizumab group at week 2. Enlarged areas of central tumor necrosis were associated with a higher ADC value. However, progressive enlargement of the tumors but no significant differences in DCE parameters or ADC were noted in the HCC827R model. These results showed that both erlotinib alone and in combination with bevacizumab could effectively inhibit tumor growth in the gefitinib-sensitive lung cancer mice model, and that this was associated with decreased vascular perfusion, increased ADC percentage, decreased microvessel density, and increased tumor apoptosis with a two-week treatment cycle.

First-In-Human Study Demonstrating Tumor-Angiogenesis by PET/CT Imaging with (68)Ga-NODAGA-THERANOST, a High-Affinity Peptidomimetic for αvβ3 Integrin Receptor Targeting

(68)Ga-NODAGA-THERANOST™ is an αvβ3 integrin antagonist and the first radiolabeled peptidomimetic to reach clinical development for targeting integrin receptors. In this first-in-human study, the feasibility of integrin receptor peptidomimetic positron emission tomography/computed tomography (PET/CT) imaging was confirmed in patients with non-small-cell lung cancer and breast cancer.

METHODS

Patients underwent PET/CT imaging with (68)Ga NODAGA-THERANOST. PET images were analyzed qualitatively and quantitatively and compared to 2-deoxy-2-((18)F) fluoro-d-glucose ((18)F-FDG) findings. Images were obtained 60 minutes postinjection of 300-500 MBq of (68)Ga-NODAGA-THERANOST.

RESULTS

(68)Ga-NODAGA-THERANOST revealed high tumor-to-background ratios (SUVmax=4.8) and uptake at neoangiogenesis sites. Reconstructed fused images distinguished cancers with high malignancy potential and enabled enhanced bone metastasis detection. (18)F-FDG-positive lung and lymph node metastases did not show uptake, indicating the absence of neovascularization.

CONCLUSIONS

(68)Ga-NODAGA-THERANOST was found to be safe and effective, exhibiting in this study rapid blood clearance, stability, rapid renal excretion, favorable biodistribution and PK/PD, low irradiation burden (μSv/MBq/μg), and convenient radiolabeling. This radioligand might enable theranostics, that is, a combination of diagnostics followed by the appropriate therapeutics, namely antiangiogenic therapy, image-guided presurgical assessment, treatment response evaluation, prediction of pathologic response, neoadjuvant-peptidomimetic-radiochemotherapy, and personalized medicine strategies. Further clinical trials evaluating (68)Ga-NODAGA-THERANOST are warranted.

Croix B, Choyke P, Jagoda EM. Immuno-PET imaging of tumor endothelial marker 8 (TEM8)

Tumor endothelial marker 8 (TEM8) is a cell surface receptor that is highly expressed in a variety of human tumors and promotes tumor angiogenesis and cell growth. Antibodies targeting TEM8 block tumor angiogenesis in a manner distinct from the VEGF receptor pathway. Development of a TEM8 imaging agent could aid in patient selection for specific antiangiogenic therapies and for response monitoring. In these studies, L2, a therapeutic anti-TEM8 monoclonal IgG antibody (L2mAb), was labeled with (89)Zr and evaluated in vitro and in vivo in TEM8 expressing cells and mouse xenografts (NCI-H460, DLD-1) as a potential TEM8 immuno-PET imaging agent. (89)Zr-df-L2mAb was synthesized using a desferioxamine-L2mAb conjugate (df-L2mAb); (125)I-L2mAb was labeled directly. In vitro binding studies were performed using human derived cell lines with high, moderate, and low/undetectable TEM8 expression. (89)Zr-df-L2mAb in vitro autoradiography studies and CD31 IHC staining were performed with cryosections from human tumor xenografts (NCI-H460, DLD-1, MKN-45, U87-MG, T-47D, and A-431). Confirmatory TEM8 Western blots were performed with the same tumor types and cells. (89)Zr-df-L2mAb biodistribution and PET imaging studies were performed in NCI-H460 and DLD-1 xenografts in nude mice. (125)I-L2mAb and (89)Zr-df-L2mAb exhibited specific and high affinity binding to TEM8 that was consistent with TEM8 expression levels. In NCI-H460 and DLD-1 mouse xenografts nontarget tissue uptake of (89)Zr-df-L2mAb was similar; the liver and spleen exhibited the highest uptake at all time points. (89)Zr-L2mAb was highly retained in NCI-H460 tumors with <10% losses from day 1 to day 3 with the highest tumor to muscle ratios (T:M) occurring at day 3. DLD-1 tumors exhibited similar pharmacokinetics, but tumor uptake and T:M ratios were reduced ∼2-fold in comparison to NCI-H460 at all time points. NCI-H460 and DLD-1 tumors were easily visualized in PET imaging studies despite low in vitro TEM8 expression in DLD-1 cells indicating that in vivo expression might be higher in DLD-1 tumors. From in vitro autoradiography studies (89)Zr-df-L2mAb specific binding was found in 6 tumor types (U87-MG, NCI-H460, T-47D MKN-45, A-431, and DLD-1) which highly correlated to vessel density (CD31 IHC). Westerns blots confirmed the presence of TEM8 in the 6 tumor types but found undetectable TEM8 levels in DLD-1 and MKN-45 cells. This data would indicate that TEM8 is associated with the tumor vasculature rather than the tumor tissue, thus explaining the increased TEM8 expression in DLD-1 tumors compared to DLD-1 cell cultures. (89)Zr-df-L2mAb specifically targeted TEM8 in vitro and in vivo although the in vitro expression was not necessarily predictive of in vivo expression which seemed to be associated with the tumor vasculature. In mouse models, (89)Zr-df-L2mAb tumor uptakes and T:M ratios were sufficient for visualization during PET imaging. These results would suggest that a TEM8 targeted PET imaging agent, such as (89)Zr-df-L2mAb, may have potential clinical, diagnostic, and prognostic applications by providing a quantitative measure of tumor angiogenesis and patient selection for future TEM8 directed therapies.

In vivo imaging of therapy-induced anti-cancer immune responses in humans

Immunotherapy aims to re-engage and revitalize the immune system in the fight against cancer. Research over the past decades has shown that the relationship between the immune system and human cancer is complex, highly dynamic, and variable between individuals. Considering the complexity, enormous effort and costs involved in optimizing immunotherapeutic approaches, clinically applicable tools to monitor therapy-induced immune responses in vivo are most warranted. However, the development of such tools is complicated by the fact that a developing immune response encompasses several body compartments, e.g., peripheral tissues, lymph nodes, lymphatic and vascular systems, as well as the tumor site itself. Moreover, the cells that comprise the immune system are not static but constantly circulate through the vascular and lymphatic system. Molecular imaging is considered the favorite candidate to fulfill this task. The progress in imaging technologies and modalities has provided a versatile toolbox to address these issues. This review focuses on the detection of therapy-induced anticancer immune responses in vivo and provides a comprehensive overview of clinically available imaging techniques as well as perspectives on future developments. In the discussion, we will focus on issues that specifically relate to imaging of the immune system and we will discuss the strengths and limitations of the current clinical imaging techniques. The last section provides future directions that we envision to be crucial for further development.