OMICS Journal of Radiology
Open Access

Endoscopy; Cancer Imaging; Scanning fiber endoscope

Introduction

Cancer continues to be a global health challenge, with early detection and accurate diagnosis playing pivotal roles in improving patient outcomes. Molecular insights via endoscopy have emerged as a promising technique, providing clinicians with unprecedented access to the molecular underpinnings of cancer. This review explores the evolution of molecular endoscopy and its diverse applications in oncology [1].

Conventional imaging modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), computed tomography (CT), and ultrasound (US) have distinct advantages and limitations. MRI detects the relaxation times of magnetic dipoles, such as hydrogen atoms in water and organic compounds, after a radiofrequency pulse, and then generates MR signals. MRI offers spatial resolution on the millimeter scale with simultaneous physiological and anatomical correlation. However, MRI requires long scan and post processing times and has relatively low sensitivity [2], thus requiring high doses (typically micrograms to milligrams) of magnetic contrast agents. PET and SPECT record high and low-energy γ− rays, respectively, emitted from within the body. These imaging modalities have very high sensitivity but relatively low spatial resolution. CT images are acquired based on the extent of X-ray absorbance by tissue. CT provides high resolution anatomical images especially for bones and tumors, but has poor soft tissue resolution and limited molecular imaging applications.

Endoscopes are thin, flexible instruments that provide a macroscopic view of the large mucosal surfaces in hollow organs internal to the human body. Miniature optics with large divergence angles is used that can generate a large field-of-view (FOV) with high spatial resolution [3]. Endo microscopy employs high numerical aperture (NA) optics to provide a small FOV with micron-level resolution for observing subcellular features. It requires scaling down the size of a conventional microscope design into a miniature package. These instruments provide a unique opportunity for early cancer detection and prevention by allowing therapy (biopsy or resection) to be performed concurrently with diagnosis.

Molecular Endoscopy: A Paradigm Shift

Traditionally, endoscopy served as a visual tool for direct examination of tissues and biopsy collection. However, the integration of molecular imaging techniques has elevated endoscopy to a new dimension. Molecular endoscopy enables real-time visualization and analysis of specific biomarkers, cellular processes, and genetic alterations associated with cancer [4].

The scanning fiber endoscope (SFE) scans in a spiral pattern by a tubular piezoelectric actuator to create an image with a large FOV. Red, green, and blue (RGB) laser light is delivered through the scanning fiber and focused onto the mucosal surface with a multi-lens assembly located in the distal tip. The reflectance and fluorescence light is collected by a ring of multimode optical fibers arranged around the perimeter of the instrument. The SFE imaging technology was first developed for early detection of cancer in the esophagus, pancreatic duct, and peripheral airways using reflected white light [5].

Applications in Gastrointestinal Oncology

Colorectal Cancer: Molecular endoscopy has transformed the early detection of colorectal cancer. Targeting molecular markers such as APC and KRAS mutations allows for precise identification of premalignant lesions and the assessment of disease progression. Esophageal and Gastric Cancer: Endoscopic molecular imaging has been instrumental in characterizing the molecular heterogeneity of esophageal and gastric cancers, guiding personalized treatment strategies [6].

Advancements in Respiratory Oncology

In lung cancer diagnosis and management, molecular endoscopy has opened new avenues:

Lung Nodules: Accurate differentiation of benign from malignant lung nodules is enhanced through the identification of specific genetic alterations like EGFR mutations and ALK rearrangements [7].

Bronchoscopic Navigation: Molecular insights via endoscopy aid in precise navigation to target lesions within the lung, facilitating biopsies and localized therapies.

Urological Oncology

Endoscopic molecular imaging has transformed urological cancer diagnosis:

Bladder Cancer: Detecting genetic mutations in bladder tumors via molecular endoscopy has revolutionized early diagnosis and treatment planning.

Prostate Cancer: Targeted biopsies based on molecular markers promise improved accuracy in prostate cancer detection [8].

Emerging Applications

Gynecological Oncology: Molecular endoscopy is shedding light on early diagnosis and targeted treatment options for ovarian and cervical cancers.

Neuroendoscopy: Exploration into the potential of molecular insights in neuroendoscopy may revolutionize brain tumor management.

Recent advances in endoscopic molecular imaging By integrating with molecular probes, endoscopes and endomicroscopes may play an expanded role in the clinic. This section reviews recent findings that show potential applications of molecular imaging for disease detection in the clinical. The two most common molecular probes that have been developed for clinical use are antibodies and peptides. Clinical use of antibodies as molecular probes has been widely explored. There are several known molecular targets for a variety of cancers, including epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), and human epidermal growth factor receptor 2. Specific antibodies to these molecular targets have been established and successfully applied in the clinic for targeted cancer therapy [9]. Alternatively, these antibodies can be utilized as targeted imaging probes. EGFR is a transmembrane glycoprotein tyrosine kinase receptor that promotes tumor proliferation, invasion, metastasis, and neovascularization. EGFR is overexpressed in roughly 25–94% of colorectal cancer cases and in most squamous cell carcinomas of the head and neck. Cetuximab and panitumumab are examples of monoclonal antibodies that bind specifically to EGFR. In one study, FITC labeled EGFR antibodies were topically applied on excised human colonic specimens. The mean fluorescence of neoplasia was significantly higher than that of normal mucosa using confocal endomicroscopy.

Challenges and Future Directions

While the prospects of molecular endoscopy are promising, several challenges persist. Standardization of protocols, integration of artificial intelligence for real-time data analysis, and expanding the repertoire of validated molecular markers remain areas of active research [10].

Conclusion

Molecular insights via endoscopy represent a transformative approach in cancer imaging. By providing real-time access to molecular information within tumors, this technique has ushered in an era of early diagnosis, personalized treatment, and improved patient outcomes across various cancer types. Continued research and technological advancements hold the potential to further elevate the role of molecular endoscopy in oncology, ultimately shaping the future of cancer care. As we look ahead, the integration of molecular insights via endoscopy promises to continue transforming the landscape of cancer imaging, bringing hope to patients and clinicians alike.

1. Khor B, Gardet A, Xavier RJ (2011) Genetics and pathogenesis of inflammatory bowel disease. Nature 474: 307-317.

Indexed at, Google Scholar, Crossref

2. Danese S, Fiocchi C (2011) Ulcerative colitis. N Engl J Med 365: 1713-1725.

Indexed at, Crossref

3. Loftus EV Jr. (2004) Clinical epidemiology of inflammatory bowel disease: incidence, prevalence, and environmental influences. Gastroenterology 126: 1504-1517.

Indexed at, Google Scholar, Crossref

4. Kaplan GG, Ng SC (2017) Understanding and preventing the global increase of inflammatory bowel disease. Gastroenterology 152: 313-321.

Indexed at, Google Scholar, Crossref

5. Matsuoka K, Kanai T (2015) The gut microbiota and inflammatory bowel disease. Semin Immunopathol 37: 47-55.

Indexed at, Google Scholar, Crossref

6. El-Serag HB, Rudolph KL (2007) Hepatocellular carcinoma: epidemiology and molecular carcinogenesis. Gastroenterology 132: 2557-2576.

Indexed at, Google Scholar, Crossref

7. Forner A, Llovet JM, Bruix J (2012) Hepatocellular carcinoma. Lancet 379: 1245-1255.

Indexed at, Crossref

8. Marrero JA, Kulik LM, Sirlin CB, Zhu AX, Finn RS, et al (2018) Diagnosis, staging, and management of hepatocellular carcinoma: 2018 practice guidance by the American Association for the Study of Liver Diseases. Hepatology 68: 723-750.

Indexed at, Google Scholar, Crossref

9. Finn RS, Qin S, Ikeda M, Galle PR, Ducreux M, et al. (2020) Atezolizumab plus Bevacizumab in Unresectable Hepatocellular Carcinoma. N Engl J Med 382: 1894-1905.

Indexed at, Google Scholar, Crossref

10. Bruix J, Takayama T, Mazzaferro V, Chau GY, Yang J, et al. (2015) Adjuvant Sorafenib for Hepatocellular Carcinoma after Resection or Ablation (STORM): a phase 3, randomised, double-blind, placebo-controlled trial. Lancet Oncol 16: 1344-1354.

Indexed at, Google Scholar, Crossref