Monitoring the effects of bevacizumab beyond progression in a murine colorectal cancer model: a functional imaging approach

Safety and Tolerability of Anti-Angiogenic Protein Kinase Inhibitors and Vascular-Disrupting Agents in Cancer: Focus on Gastrointestinal Malignancies

Angiogenesis is an essential process for tumor growth and metastasis. Inhibition of angiogenesis as an anticancer strategy has shown significant results in a plethora of tumors. Anti-angiogenic agents are currently part of many standard-of-care options for several metastatic gastrointestinal cancers. Bevacizumab, aflibercept, ramucirumab, and regorafenib have significantly improved both progression-free and overall survival in different lines of treatment in metastatic colorectal cancer. Second-line ramucirumab and third-line apatinib are effective anti-angiogenic treatments for patients with metastatic gastric cancer. Unfortunately, the anti-angiogenic strategy has major practical limitations: resistance inevitably develops through redundancy of signaling pathways and selection for subclonal populations adapted for hypoxic conditions. Anti-angiogenic agents may be more effective in combination therapies, with not only cytotoxics but also other emerging compounds in the anti-angiogenic class or in the separate class of the so-called vascular-disrupting agents. This review aims to provide an overview of the approved and "under development" anti-angiogenic compounds as well as the vascular-disrupting agents in the treatment of gastrointestinal cancers, focusing on the actual body of knowledge available on therapy challenges, pharmacodynamic and pharmacokinetic mechanisms, safety profiles, promising predictive biomarkers, and future perspectives.

Early prediction of tumor response to bevacizumab treatment in murine colon cancer models using three-dimensional dynamic contrast-enhanced ultrasound imaging

Due to spatial tumor heterogeneity and consecutive sampling errors, it is critically important to assess treatment response following antiangiogenic therapy in three dimensions as two-dimensional assessment has been shown to substantially over- and underestimate treatment response. In this study, we evaluated whether three-dimensional (3D) dynamic contrast-enhanced ultrasound (DCE-US) imaging allows assessing early changes in tumor perfusion following antiangiogenic treatment (bevacizumab administered at a dose of 10 mg/kg b.w.), and whether these changes could predict treatment response in colon cancer tumors that either are responsive (LS174T tumors) or none responsive (CT26) to the proposed treatment. Our results showed that the perfusion parameters of 3D DCE-US including peak enhancement (PE) and area under curve (AUC) significantly decreased by up to 69 and 77%, respectively, in LS174T tumors within 1 day after antiangiogenic treatment (P = 0.005), but not in CT26 tumors (P > 0.05). Similarly, the percentage area of neovasculature significantly decreased in treated versus control LS174T tumors (P < 0.001), but not in treated versus control CT26 tumors (P = 0.796). Early decrease in both PE and AUC by 45-50% was predictive of treatment response in 100% (95% CI 69.2, 100%) of responding tumors, and in 100% (95% CI 88.4, 100%) and 86.7% (95% CI 69.3, 96.2%), respectively, of nonresponding tumors. In conclusion, 3D DCE-US provides clinically relevant information on the variability of tumor response to antiangiogenic therapy and may be further developed as biomarker for predicting treatment outcomes.

A minimum core outcome dataset for the reporting of preclinical chemotherapeutic drug studies: Lessons learned from multiple discordant methodologies in the setting of colorectal cancer

In vivo studies in animal models are critical tools necessary to study the fundamental complexity of carcinogenesis. A constant strive to improve animal models in cancer exists, especially those investigating the use of chemotherapeutic effectiveness. In the present systematic review, colorectal cancer (CRC) is used as an example to highlight and critically evaluate the range of reporting strategies used when investigating chemotherapeutic agents in the preclinical setting. A systematic review examining the methodology and reporting of preclinical chemotherapeutic drug studies using CRC murine models was conducted. A total of 45 studies were included in this systematic review. The literature was found to be highly heterogeneous with various cell lines, animal strains, animal ages and chemotherapeutic compounds/regimens tested, proving difficult to compare outcomes between similar studies or indeed gain any significant insight into which chemotherapeutic regimen caused adverse events. From this analysis we propose a minimum core outcome dataset that could be regarded as a standardised way of reporting results from in vivo experimentation.

Early Assessment of Colorectal Cancer Patients with Liver Metastases Treated with Antiangiogenic Drugs: The Role of Intravoxel Incoherent Motion in Diffusion-Weighted Imaging

Purpose

To assess the feasibility and effectiveness of quantitative intravoxel incoherent motion (IVIM) of Diffusion-weighted imaging (DWI) in the assessment of liver metastases treated with targeted chemotherapy agents.

Methods

12 patients with unresectable liver metastases from colorectal cancer were enrolled and received neoadjuvant FOLFIRI (5-fluorouracil, leucovorin, irinotecan) plus bevacizumab therapy. DWI was performed for 36 metastases at baseline and after 14 days from starting the treatment. In addition to the basic IVIM metrics, the product between pseudo-diffusivity and perfusion fraction was considered as a descriptor roughly analogous to the flow. Median diffusion parameters of Region of Interest (ROI) were used as representative values for each lesion. Normalized parameters in comparison with the median value of spleen were also collected. The percentual change of the diffusion parameters was calculated. The response to chemotherapy was evaluated according the Response Evaluation Criteria in Solid Tumors (RECIST) as calculated on whole-body CT scan obtained three months after treatment. Mann Whitney test and Receiver operating characteristic (ROC) analysis were performed.

Results

24 lesions were categorized as responding and 12 as not responding. There was no statistically significant difference among absolute and normalized diffusion parameters between the pretreatment and the post-treatment findings. Instead, the perfusion fraction (f_p) values showed a statistical difference between responder and non-responder lesions: sensitivity and specificity of f_p variation was 62% and 93%, respectively.

Conclusions

IVIM parameters represent a valuable tool in the evaluation of the anti-angiogenic therapy in patients with liver metastases from colorectal cancer. A percentage change of f_p represents the most effective DWI marker in the assessment of tumor response.

Optimal duration of systemic treatment in metastatic colorectal cancer

PURPOSE OF REVIEW

With the currently available cytotoxic and targeted drugs, metastatic colorectal cancer (mCRC) may be controlled by systemic treatment for a significant period of time. However, many questions remain about the optimal use of drugs and duration of treatment. We reviewed the data from clinical trials on the optimal duration of systemic treatment with chemotherapy and targeted therapy in mCRC patients.

RECENT FINDINGS

The feasibility of chemotherapy-free intervals has been studied in mCRC patients treated with chemotherapy alone, but the results are conflicting. Current data show that oxaliplatin may be safely interrupted, but do not allow a firm conclusion on the safety of a full treatment break of chemotherapy. For targeted therapy, continuous inhibition of intracellular signalling by prolonged administration would theoretically be beneficial for efficacy of treatment, and has been suggested by retrospectively collected data. Recent data from a prospective study show a clinical benefit for maintenance treatment with chemotherapy and bevacizumab with acceptable toxicity and preservation of quality of life. Survival benefits were seen in selected patient subgroups. No data on the optimal duration of treatment with anti-epidermal growth factor receptor agents are currently available.

SUMMARY

There are no definite data on the safety of chemotherapy-free intervals. Data on targeted therapy support the use of maintenance treatment of chemotherapy plus bevacizumab.

Systemic treatment: maintenance compared with holiday

With the currently available cytotoxic and targeted drugs, metastatic colorectal cancer (mCRC) may be controlled by systemic treatment for a substantial period of time. However, many questions remain about the optimal use of drugs and duration of treatment. The feasibility of chemotherapy-free intervals has been studied in patients with mCRC treated with chemotherapy alone, but the results are conflicting. Current data show that oxaliplatin may be safely interrupted, but they do not allow a firm conclusion on the safety of a full treatment break of chemotherapy. For targeted therapy, continuous inhibition of intracellular signaling by prolonged administration would theoretically be beneficial for efficacy of treatment. Recent data support the use of maintenance treatment with chemotherapy and bevacizumab. No data on the optimal duration of treatment with anti-epidermal growth factor receptor (EGFR) agents are currently available.

The "angiogenetic ladder", step-wise angiogenesis inhibition in metastatic colorectal cancer

The number of anti-angiogenic drugs who demonstrated activity in metastatic colorectal cancer patients is arising but there is still much debate on which is the optimal use of this class of agents, with particular emphasis given on when (meant as in which line of treatment) and how (meant as in duration of treatment). We sampled the data of randomised phase II-III trials employing this type of drugs, with particular emphasis on trying to "highlight" situations where anti-angiogenetic treatment could provide most benefit. The review displays all relevant clinical data regarding the use of anti-angiogenic drugs in metastatic colorectal cancer and comments on potential implications of these trials in everyday clinical practice.