In vivo assessment of tumour angiogenesis in colorectal cancer: the role of confocal laser endomicroscopy

Current trends in the characterization and monitoring of vascular response to cancer therapy

Tumor vascular physiology is an important determinant of disease progression as well as the therapeutic outcome of cancer treatment. Angiogenesis or the lack of it provides crucial information about the tumor's blood supply and therefore can be used as an index for cancer growth and progression. While standalone anti-angiogenic therapy demonstrated limited therapeutic benefits, its combination with chemotherapeutic agents improved the overall survival of cancer patients. This could be attributed to the effect of vascular normalization, a dynamic process that temporarily reverts abnormal vasculature to the normal phenotype maximizing the delivery and intratumor distribution of chemotherapeutic agents. Longitudinal monitoring of vascular changes following antiangiogenic therapy can indicate an optimal window for drug administration and estimate the potential outcome of treatment. This review primarily focuses on the status of various imaging modalities used for the longitudinal characterization of vascular changes before and after anti-angiogenic therapies and their clinical prospects.

Analysis of the Characteristics of Coexisting Lesions in Colorectal Cancer Patients in an International Study: A Subgroup Analysis of the ATLAS Trial

INTRODUCTION

We investigated coexisting lesion types in patients with invasive colorectal cancer (CRC) in a multinational study for comprehending the adenoma-carcinoma and serrated pathway about the development of CRC.

METHODS

We retrospectively reviewed 3,050 patients enrolled in the international randomized controlled trial (ATLAS study) to evaluate the colorectal polyp detection performance of image-enhanced endoscopy in 11 institutions in four Asian countries/regions. In the current study, as a subgroup analysis of the ATLAS study, 92 CRC patients were extracted and compared to 2,958 patients without CRC to examine the effects of age, sex, and coexisting lesion types (high-grade adenoma [HGA], low-grade adenoma with villous component [LGAV], 10 adenomas, adenoma ≥10 mm, sessile serrated lesions [SSLs], and SSLs with dysplasia [SSLD]). Additional analyses of coexisting lesion types were performed according to sex and location of CRC (right- or left-sided).

RESULTS

A multivariate analysis showed that HGA (odds ratio [95% confidence interval] 4.29 [2.16-8.18]; p < 0.01), LGAV (3.02 [1.16-7.83], p = 0.02), and age (1.04 [1.01-1.06], p = 0.01) were independently associated with CRC. According to sex, the coexisting lesion types significantly associated with CRC were LGAV (5.58 [1.94-16.0], p < 0.01) and HGA (4.46 [1.95-10.20], p < 0.01) in males and HGA (4.82 [1.47-15.80], p < 0.01) in females. Regarding the location of CRC, SSLD (21.9 [1.31-365.0], p = 0.03) was significant for right-sided CRC, and HGA (5.22 [2.39-11.4], p < 0.01) and LGAV (3.46 [1.13-10.6], p = 0.02) were significant for left-sided CRC.

CONCLUSIONS

The significant coexisting lesions in CRC differed according to sex and location. These findings may contribute to comprehending the pathogenesis of CRC.

Moxifloxacin as a contrast agent of two-photon microscopic imaging for detecting colorectal diseases

Since two-photon microscopy (TPM) can obtain high-resolution images at cellular and subcellular level and moxifloxacin has multiphoton fluorescence characteristic, our study aimed to explore the feasibility and diagnostic value of moxifloxacin-assisted TPM in different human colorectal diseases, including low-grade intraepithelial neoplasia (LGIN), high-grade intraepithelial neoplasia (HGIN) and cancer tissues. Excitation power for TPM imaging with and without moxifloxacin was (2.74 ± 0.16) mW and (0.28 ± 0.02) mW, respectively (p < 0.05). Whether labeled with moxifloxacin or not, images of normal, LGIN, HGIN and cancer tissues all reached the strongest signal at 30 μm from the mucosa. Normalized fluorescence intensity of TPM images with moxifloxacin was approximately 10 times stronger than that without moxifloxacin. Fluorescence signal was differed significantly in normal, LGIN, HGIN and cancer tissues with or without moxifloxacin (p < 0.05). Besides, moxifloxacin-assisted TPM could present variant tissue features with different colorectal diseases, such as the crypt opening, glandular structure, adjacent glandular space and fluorescence distribution.

Endorectal Ultrasonography and Pelvic Magnetic Resonance Imaging Show Similar Diagnostic Accuracy in Local Staging of Rectal Cancer: An Update Systematic Review and Meta-Analysis

BACKGROUND

Endorectal Ultrasonography (EUS-ERUS) and pelvic magnetic resonance imaging (MRI) are world-wide performed for the local staging of rectal cancer (RC), but no clear consensus on their indications is present, there being literature in support of both. The aim of this meta-analysis is to give an update regarding the diagnostic test accuracy of ERUS and pelvic MRI about the local staging of RC.

MATERIALS AND METHODS

A systematic literature search from November 2020 to October 2021 was performed to select studies in which head-to-head comparison between ERUS and MRI was reported for the local staging of rectal cancer. Quality and risk of bias were assessed with the QUADAS-2 tool. Our primary outcome was the T staging accuracy of ERUS and MRI for which pooled accuracy indices were calculated using a bivariable random-effects model. In addition, a hierarchical summary receiver operating characteristic curve (hSROC) was created to characterize the accuracy of ERUS and MRI for the staging of T and N parameters. The area under the hSROC curve (AUChSROC) was determined as a measure of diagnostic accuracy.

RESULTS

Seven studies and 331 patients were included in our analysis. ERUS and MRI showed a similar accuracy for the T staging, with AUChSROC curves of 0.91 (95% C.I., 0.89 to 0.93) and 0.87 (95% C.I., 0.84 to 0.89), respectively (p = 0.409). For T staging, ERUS showed a pooled sensitivity of 0.82 (95% C.I. 0.72 to 0.89) and pooled specificity of 0.91 (95% C.I. 0.77-0.96), while MRI had pooled sensitivity and specificity of 0.69 (95% C.I. 0.55-0.81) and 0.88 (95% C.I. 0.79-0.93), respectively. ERUS and MRI showed a similar accuracy in the N staging too, with AUChSROC curves of 0.92 (95% C.I., 0.89 to 0.94) and 0.93 (95% C.I., 0.90 to 0.95), respectively (p = 0.389).

CONCLUSIONS

In conclusion, ERUS and MRI are comparable imaging techniques for the local staging of rectal cancer.

Vascular Normalization: A New Window Opened for Cancer Therapies

Preclinical and clinical antiangiogenic approaches, with multiple side effects such as resistance, have not been proved to be very successful in treating tumor blood vessels which are important targets for tumor therapy. Meanwhile, restoring aberrant tumor blood vessels, known as tumor vascular normalization, has been shown not only capable of reducing tumor invasion and metastasis but also of enhancing the effectiveness of chemotherapy, radiation therapy, and immunotherapy. In addition to the introduction of such methods of promoting tumor vascular normalization such as maintaining the balance between proangiogenic and antiangiogenic factors and targeting endothelial cell metabolism, microRNAs, and the extracellular matrix, the latest molecular mechanisms and the potential connections between them were primarily explored. In particular, the immunotherapy-induced normalization of blood vessels further promotes infiltration of immune effector cells, which in turn improves immunotherapy, thus forming an enhanced loop. Thus, immunotherapy in combination with antiangiogenic agents is recommended. Finally, we introduce the imaging technologies and serum markers, which can be used to determine the window for tumor vascular normalization.

Serrated lesions of the colon and rectum: Emergent epidemiological data and molecular pathways

In 2010, serrated polyps (SP) of the colon have been included in the WHO classification of digestive tumors. Since then a large corpus of evidence focusing on these lesions are available in the literature. This review aims to analyze the present data on the epidemiological and molecular aspects of SP. Hyperplastic polyps (HPs) are the most common subtype of SP (70-90%), with a minimal or null risk of malignant transformation, contrarily to sessile serrated lesions (SSLs) and traditional serrated adenomas (TSAs), which represent 10-20% and 1% of adenomas, respectively. The malignant transformation, when occurs, is supported by a specific genetic pathway, known as the serrated-neoplasia pathway. The time needed for malignant transformation is not known, but it may occur rapidly in some lesions. Current evidence suggests that a detection rate of SP ≥15% should be expected in a population undergoing screening colonoscopy. There are no differences between primary colonoscopies and those carried out after positive occult fecal blood tests, as this screening test fails to identify SP, which rarely bleed. Genetic similarities between SP and interval cancers suggest that these cancers could arise from missed SP. Hence, the detection rate of serrated-lesions should be evaluated as a quality indicator of colonoscopy. There is a lack of high-quality longitudinal studies analyzing the long-term risk of developing colorectal cancer (CRC), as well as the cancer risk factors and molecular tissue biomarkers. Further studies are needed to define an evidence-based surveillance program after the removal of SP, which is currently suggested based on experts' opinions.

The Role of Micro-RNAs and Circulating Tumor Markers as Predictors of Response to Neoadjuvant Therapy in Locally Advanced Rectal Cancer

The response to neoadjuvant chemoradiation (nCRT) is a critical step in the management of locally advanced rectal cancer (LARC) patients. Only a minority of LARC patients responds completely to neoadjuvant treatments, thus avoiding invasive radical surgical resection. Moreover, toxic side effects can adversely affect patients' survival. The difficulty in separating in advances responder from non-responder patients affected by LARC highlights the need for valid biomarkers that guide clinical decision-making. In this context, microRNAs (miRNAs) seem to be promising candidates for predicting LARC prognosis and/or therapy response, particularly due to their stability, facile detection, and disease-specific expression in human tissues, blood, serum, or urine. Although a considerable number of studies involving potential miRNA predictors to nCRT have been conducted over the years, to date, the identification of the perfect miRNA signatures or single miRNA, as well as their use in the clinical practice, is still representing a challenge for the management of LARC patients. In this review, we will first introduce LARC and its difficult management. Then, we will trace the scientific history and the key obstacles for the identification of specific miRNAs that predict responsiveness to nCRT. There is a high potential to identify non-invasive biomarkers that circulate in the human bloodstream and that might indicate the LARC patients who benefit from the watch-and-wait approach. For this, we will critically evaluate recent advances dealing with cell-free nucleic acids including miRNAs and circulating tumor cells as prognostic or predictive biomarkers.

Potential applications of artificial intelligence in colorectal polyps and cancer: Recent advances and prospects

Since the advent of artificial intelligence (AI) technology, it has been constantly studied and has achieved rapid development. The AI assistant system is expected to improve the quality of automatic polyp detection and classification. It could also help prevent endoscopists from missing polyps and make an accurate optical diagnosis. These functions provided by AI could result in a higher adenoma detection rate and decrease the cost of polypectomy for hyperplastic polyps. In addition, AI has good performance in the staging, diagnosis, and segmentation of colorectal cancer. This article provides an overview of recent research focusing on the application of AI in colorectal polyps and cancer and highlights the advances achieved.

Label-free multiphoton microscopic imaging as a novel real-time approach for discriminating colorectal lesions: A preliminary study

BACKGROUND AND AIM

Although various endoscopic technologies have been developed to increase the visual diagnostic accuracy of colorectal precancerosis and early carcinoma, the biopsy-dependent pathology still remains the golden standard. During routine endoscopy, real-time optical histological diagnosis is desired. Without fluorescent label, multiphoton microscopy (MPM) imaging directly reveals live cellular morphology and tissue microenvironment based on intrinsic two-photon excited fluorescence and second harmonic generation signals. Its high-imaging resolution and performance are comparable with the histopathology. We thus aimed to initially investigate the original features of colorectal diseases under MPM and evaluate its potential for real-time diagnosis.

METHODS

Experimental and diagnostic cohorts were designed. Multiphoton images of 40 ex vivo fresh tissues confirmed pathologically of colorectal normal tissues, hyperplastic polyps, adenomas, and adenocarcinomas were collected. Features were recorded to establish diagnostic standards with MPM. For the second cohort with 92 fresh tissues, we distinguished the various colorectal diseases with conclusive MPM features.

RESULTS

Through the investigation, the colorectal diseases were presented differences in the crypt opening, gland structure, epithelial cells, and collagen fibers. With the typical features, we preliminarily tested the diagnostic efficiency and found that its sensitivity for distinguishing normal, hyperplastic polyps, adenoma and adenocarcinoma was 88.89%, 76.47%, 83.33%, and 97.92%, while the specificity was 99.32%, 94.00%, 94.92%, and 94.12%, respectively.

CONCLUSION

The real-time multiphoton microscopic imaging can be effective to identify the colorectal lesions with high resolution. Via integrating with the endoscopes in the future, it could promote precise optical diagnosis in clinics.

Shedding light on fibered confocal fluorescence microscopy: Applications in biomedical imaging and therapies

Discoveries of major importance in life sciences and preclinical research are linked to the invention of microscopes that enable imaging of cells and their microstructures. Imaging technologies involving in vivo procedures using fluorescent dyes that permit labelling of cells have been developed over the last two decades. Fibered confocal fluorescence microscopy (FCFM) is an imaging technology equipped with fiber-optic probes to deliver light to organs and tissues of live animals. This enables not only in vivo detection of fluorescent signals and visualization of cells, but also the study of dynamic processes, such cell proliferation, apoptosis and angiogenesis, under physiological and pathological conditions. This will allow the diagnosis of diseased organs and tissues and the evaluation of the efficacy of new therapies in animal models of human diseases. The aim of this report is to shed light on FCFM and its potential medical applications and discusses some factors that compromise the reliability and reproducibility of monitoring biological processes by FCFM. This report also highlights the issues concerning animal experimentation and welfare, and the contributions of FCFM to the 3Rs principals, replacement, reduction and refinement.

Oncological Outcomes and Quality of Life After Rectal Cancer Surgery

Surgery for rectal cancer has been completely revolutionized thanks to the adoption of new technologies and up-to-date surgical procedures that have been applied to the traditional milestone represented by Total Mesorectal Excision (TME). The multimodal and multidisciplinary approach, with new technologies increased the patients' life expectancies; nevertheless, they have placed the surgeon in front of newer issues, represented by both oncological outcomes and the patients' need of a less destructive surgery and improved quality of life. In this review we will go through laparoscopic, robotic and transanal TME surgery, to show how the correct choice of the most appropriate technique, together with a deep knowledge of oncological principles and pelvic anatomy, is crucial to pursue an optimal cancer treatment. Novel technologies might also help to decrease the patients' fear of surgery and address important issues such as cosmesis and improved preservation of postoperative functionality.

Spontaneous intracardiac microcavitations in a patient with a colonic carcinoma

Intracardiac microcavitations consist of airy microbubbles. They are typically found in patients with an intravascular line or device, mechanical heart valves or in decompression sickness. We report a case of a patient in mid-70s who was admitted due to weakness in both legs, left-thoracic pain and fever. Despite the lack of any of the risk factors mentioned above, spontaneous microcavitations were detected in the right sided cardiac cavities. After the detection of liver lesions suspicious for a metastatic disease, a colonoscopy was performed. An ulcerated colonic carcinoma at the ileocoecal valve was diagnosed and highly suspicious for being the entry port of the microcavitations. This unusual presentation of microcavitations together with a colonic neoplasia leads to hypotheses about the journey of the microbubbles from the ascending colon into the right heart. Gastrointestinal tumours are described as being the causes of microbubbles. Translocation of microbubbles through hepatopulmonary shunting are described in the context of locally applied particles of similar size during radioembolisation. A thorough aetiological workup is of importance since the underlying cause is potentially dangerous due to its own nature of disease and due the complications of the microcavitations such as paradoxical emboli or pulmonary sequelae.

Serrated Lesions of the Colon-Rectum: A Focus on New Diagnostic Tools and Current Management

Prompt diagnosis and correct management of the so called "serrated lesions" (SLs) of the colon-rectum are generally considered of crucial importance in the past years, mainly due to their histological heterogeneity and peculiar clinical and molecular patterns; sometimes, they are missed at conventional endoscopy and are possibly implicated in the genesis of interval cancers. The aim of this review is to focus on the diagnostic challenges of serrated lesions, underlying the role of both conventional endoscopy and novel technologies. We will show how an accurate and precise diagnosis should immediately prompt the most appropriate therapy other than defining a proper follow-up program. It will be emphasized how novel endoscopic techniques may provide better visualization of mucosal microsurface structures other than enhancing the microvascular architecture, in order to better define and characterize specific patterns of mucosal lesions of the gastrointestinal tract. Standard therapy of SLs of the colon-rectum is still very debated, also due to the relatively lack of studies focusing on treatment issues. The high risk of incomplete resection, together with the high rate of postcolonoscopy interval cancers, suggests the need of an extra care when facing this kind of lesions. Given this background, we will outline useful technical tips and tricks in the resection of SLs, taking aspects such as the size and location of the lesions, as well as novel available techniques and technologies, other than future perspectives, including confocal laser endomicroscopy into consideration. Follow-up of SLs is another hot topic, also considering that their clinical impact has been misunderstood for a long time. The incidence of the so called interval colorectal cancer underlines how some weaknesses exist in current screening and follow-up programs. Considering the lack of wide consensus for the management of some SLs, we will try to summarize and clarify the best strategies for their optimal management.

Antiangiogenic therapy: Markers of response, "normalization" and resistance

Currently in cancer treatment, one premise is to use antiangiogenic therapies in association with chemotherapy or radiotherapy to augment their efficacy by benefiting from the vascular "normalization" induced by antiangiogenic therapy. This concept defines the time during which the tumor blood vessels adopt normal-like morphology and functionality, i.e. the blood vessels become more mature, the perfusion augments and hypoxia decreases. To date, there is such a diversity of treatment protocols where the type of antiangiogenic to adopt, its dose and duration of administration are different, that knowing when and how to treat is problematic. In this review, we analyzed thoroughly preclinical and clinical studies that use antiangiogenic treatments to benefit from the "normalization" and showed that the effects depend on the type of antiangiogenic administrated (anti-VEGF, anti-VEGFR, Multi-Kinase Inhibitor) and on the duration of treatment. Finally, biomarkers of "normalization" and resistance that could be used in the clinic are presented.

K-ras Mutations as the Earliest Driving Force in a Subset of Colorectal Carcinomas

K-ras oncogene is a key factor in colorectal cancer. Based on published and our data we propose that K-ras could be the oncogene responsible for the inactivation of the tumor-suppressor gene APC, currently considered as the initial step in colorectal tumorigenesis. K-ras fulfills the criteria of the oncogene-induced DNA damage model, as it can provoke well-established causes for inactivating tumor-suppressors, i.e. DNA double-strand breaks (causing allele deletion) and ROS production (responsible for point mutation). The model we propose is a variation of the currently existing model and hypothesizes that, in a subgroup of colorectal carcinomas, K-ras mutation may precede APC inactivation, representing the earliest driving force and, probably, an early biomarker of colorectal carcinogenesis. This observation is clinically useful, since it may modify the preventive colorectal cancer strategy, restricting numerically patients undergoing colonoscopies to those bearing K-ras mutation in their colorectum, either in benign polyps or the normal accompanying mucosa.

Probe-based confocal laser endomicroscopy for in vivo evaluation of the tumor vasculature in gastric and rectal carcinomas

Probe-based Confocal Laser Endomicroscopy (pCLE) is a powerful imaging technique that allows to perform gastrointestinal endomicroscopy at subcellular resolution. The aim of this study was to assess the use of pCLE to evaluate tumor angiogenesis in rectal and gastric cancers. A total of 35 consecutive patients with gastric and 91 with rectal carcinomas underwent endoscopy and pCLE during the same examination. Vascular assessment was based on vessel shape and size, vessel permeability and blood flow, and allowed the creation of an angiogenic score ranging from 0, for normal vasculature, to 4, for aberrant vasculature. A significant difference for the presence of vessels with large diameter and defective blood flow was found between rectal and gastric cancers. Overall, rectal cancers displayed a higher angiogenic score compared to gastric cancers. Conventional therapy induced a striking reduction in the angiogenic score only in rectal cancer patients. Taken together, our findings suggest that the pCLE technology is suitable for the evaluation of the tumor microvasculature abnormalities. Therefore, the real-time assessment of the vasculature status may represent a promising approach to predict the efficacy of the treatments and improve the clinical management of patients with gastric or rectal carcinomas.

Confocal laser endomicroscopy in ulcerative colitis: beyond endoscopic assessment of disease activity

BACKGROUND

The aim of this study was to investigate the role of confocal laser endomicroscopy (CLE) in the assessment of disease activity in ulcerative colitis (UC).

METHODS

Consecutive patients with UC referred to our inflammatory bowel disease unit for colonoscopy were enrolled. Patients without UC were used as controls. UC activity was evaluated by white light endoscopy and classified according to the Mayo Ulcerative Colitis Endoscopic Score of Severity. Endoscopic biopsies were also taken for histological assessment of disease activity and then assessed with CLE. Three parameters were evaluated; crypt architecture (crypt diameter, inter-crypt distance, presence of fused crypts, crypts regularity), microvascular pattern (regular, dilated, irregular and deformed), fluorescein leakage.

RESULTS

Fifty patients with UC and 10 controls were enrolled. At colonoscopy, 11 patients (22%), 19 patients (38%), 12 patients (24%) and 8 patients (16%) presented a Mayo score of 0, 1, 2 and 3, respectively. At CLE, fused crypts were present in all the patients with UC and absent in controls. Crypt diameter and inter-crypt distance showed a parallel increase with the Mayo score. Fluorescein leakage and irregular vessels were more frequently found in case of a high level of endoscopic severity, but were also identified in about 20% of UC patients with normal mucosa. Biopsies also demonstrated the presence of histological activity in 4 patients with endoscopically inactive colitis.

CONCLUSIONS

CLE might be a useful tool to determine inflammatory activity in UC. Fused crypts appeared to be a CLE marker of UC, while other abnormalities, like microvascular alteration and fluorescein leakage, have also been identified in patients with mucosal healing at endoscopy. Larger series are required to validate these results and the advantages of a CLE-based assessment of UC activity.