Colorectal cancer (CRC) is one of the most common cancers worldwide. These malignancies originate in the colon or rectum, and the majority evolve from pre-existing colonic adenomas (a type of colon polyp). Early detection, identification, and removal of these precancerous lesions can effectively reduce the morbidity and mortality of colorectal cancer.

However, not all colonic polyps possess a significant risk of malignant transformation. Polyps can generally be subdivided into "neoplastic" and "non-neoplastic" lesions; major non-neoplastic polyps include inflammatory polyps, hamartomas, lymphoid polyps, mucosal prolapse polyps, and hyperplastic polyps. On the other hand, neoplastic polyps have the potential to develop into malignancies, primarily including adenomatous polyps and serrated polyps. Adenomatous polyps account for more than 50% of all colonic polyps and are the most common precancerous lesions for CRC. Clinically, they can be further classified into tubular, tubulovillous, or villous adenomas based on histological subtypes. As for serrated polyps, traditional serrated adenomas (TSAs) and sessile serrated lesions (SSLs) possess carcinogenic potential.

During a colonoscopy, detecting colonic polyps is crucial, but it is equally important to identify which polyps have malignant potential. This allows for the accurate resection of true precancerous lesions while avoiding the procedural risks associated with unnecessary polypectomies. Furthermore, in rare instances, diminutive polyps may harbor cancer with deep submucosal invasion. Due to the risks of incomplete resection and lymph node metastasis, such lesions are not suitable for endoscopic resection. Therefore, achieving an accurate endoscopic diagnosis is a key step in determining the most appropriate management strategy for colonic polyps.

To improve the diagnostic accuracy of endoscopy for colonic polyps, multiple modalities have been developed, including careful observation of lesion morphology, as well as various image-enhanced technologies and chromoendoscopy. Meanwhile, three-dimensional (3D) endoscopy, a novel technology, offers superior spatial resolution and depth perception compared to conventional two-dimensional (2D) endoscopy. Studies have confirmed that 3D endoscopy can improve the adenoma detection rate (ADR) due to its enhanced ability to detect flat and inconspicuous lesions. However, whether 3D colonoscopy can also enhance the endoscopic diagnostic accuracy for colonic polyps remains to be explored. Therefore, we designed a randomized controlled trial (RCT) to investigate whether 3D colonoscopy can improve the diagnostic accuracy of colonic polyps compared to conventional 2D colonoscopy.

Colorectal cancer (CRC) is one of the most common cancers worldwide. These malignancies originate in the colon or rectum, and the majority evolve from pre-existing colonic adenomas (a type of colon polyp). Early detection, identification, and removal of these precancerous lesions can effectively reduce the morbidity and mortality of colorectal cancer.

However, not all colonic polyps possess a significant risk of malignant transformation. Polyps can generally be subdivided into "neoplastic" and "non-neoplastic" lesions; major non-neoplastic polyps include inflammatory polyps, hamartomas, lymphoid polyps, mucosal prolapse polyps, and hyperplastic polyps. On the other hand, neoplastic polyps have the potential to develop into malignancies, primarily including adenomatous polyps and serrated polyps. Adenomatous polyps account for more than 50% of all colonic polyps and are the most common precancerous lesions for CRC. Clinically, they can be further classified into tubular, tubulovillous, or villous adenomas based on histological subtypes. As for serrated polyps, traditional serrated adenomas (TSAs) and sessile serrated lesions (SSLs) possess carcinogenic potential.

During a colonoscopy, detecting colonic polyps is crucial, but it is equally important to identify which polyps have malignant potential. This allows for the accurate resection of true precancerous lesions while avoiding the procedural risks associated with unnecessary polypectomies. Furthermore, in rare instances, diminutive polyps may harbor cancer with deep submucosal invasion. Due to the risks of incomplete resection and lymph node metastasis, such lesions are not suitable for endoscopic resection. Therefore, achieving an accurate endoscopic diagnosis is a key step in determining the most appropriate management strategy for colonic polyps.

To improve the diagnostic accuracy of endoscopy for colonic polyps, multiple modalities have been developed, including careful observation of lesion morphology, as well as various image-enhanced technologies and chromoendoscopy. Meanwhile, three-dimensional (3D) endoscopy, a novel technology, offers superior spatial resolution and depth perception compared to conventional two-dimensional (2D) endoscopy. Studies have confirmed that 3D endoscopy can improve the adenoma detection rate (ADR) due to its enhanced ability to detect flat and inconspicuous lesions. However, whether 3D colonoscopy can also enhance the endoscopic diagnostic accuracy for colonic polyps remains to be explored. Therefore, we designed a randomized controlled trial (RCT) to investigate whether 3D colonoscopy can improve the diagnostic accuracy of colonic polyps compared to conventional 2D colonoscopy.

This study is a single-country, multicenter randomized controlled trial (RCT), expected to be conducted at National Taiwan University Hospital, National Taiwan University Cancer Center, NTUH Hsinchu Branch, and Chia-Yi Christian Hospital. The trial includes an experimental group (observed first with 3D endoscopy, then with conventional 2D endoscopy) and a control group (observed first with conventional 2D endoscopy, then with 3D endoscopy). As an exploratory study, we plan to enroll 600 adults aged 18 and above undergoing colonoscopy, randomized in a 1:1 ratio into the experimental and control groups. All endoscopists participating in this research project have extensive endoscopic experience, performing at least 100 polypectomies annually. Informed consent will be obtained in the outpatient clinic and the endoscopy center. When a patient requires a colonoscopy, the principal investigator will inquire about their willingness to join the clinical study in the clinic or the endoscopy room. If the subject is willing to participate, a research assistant will help explain the study and assist with the signing of the informed consent form.

When subjects undergo the colonoscopy, the operator will use the conventional 2D endoscopic mode for insertion. Once the colonoscope reaches the cecum, a research assistant will randomly assign the subject to one of the two endoscopic modality sequences using a sealed envelope, with an expected 1:1 allocation ratio between the two groups. The primary difference between the two groups occurs during the withdrawal of the endoscope from the cecum to the anus. If a polyp lesion is detected, one group will first use conventional 2D imaging for polyp diagnosis, and then switch to 3D endoscopy for a second diagnosis. The other group will do the reverse: completing the diagnosis with 3D endoscopy first, and then switching to conventional 2D endoscopy for a second diagnosis. This design aims to eliminate judgment bias caused by the diagnostic sequence. The resected polyps will be sent to the pathology department for histopathological examination. Subsequently, the pathological diagnosis will be compared with both the 3D and 2D endoscopic diagnoses to determine the endoscopic diagnostic accuracy for each, defined as the diagnostic consistency rate between the endoscopic and pathological diagnoses. Regardless of the subject's assigned group, the operator will utilize other image-enhanced techniques (such as NBI or chromoendoscopy) and perform polypectomies according to routine clinical practice during the withdrawal phase.

Endpoints:

Primary Endpoints: The primary endpoint of this study is to compare the diagnosis accuracy rate (DAR) of polyps under different endoscopic modes to determine if there is a significant difference between 3D and 2D colonoscopy. This is primarily calculated by comparing the pathological diagnosis of the resected polyps sent for laboratory testing with the 3D and 2D endoscopic diagnoses, which represents the diagnostic consistency rate. In practical application, each polyp will receive a 3D diagnosis and a 2D diagnosis (regardless of the order), as well as a pathological diagnosis. If the 3D diagnosis of a polyp aligns with the pathological diagnosis, it is considered a correct diagnosis; otherwise, it is deemed incorrect. The DAR is the proportion of correct diagnoses out of the total number of polyps analyzed.

Secondary Endpoints: The secondary endpoints will evaluate the diagnosis alternation rate, which is the frequency of inconsistent endoscopic diagnoses for the same polyp when utilizing different observation methods. Additionally, the impact of factors such as the sizes of polyps, morphology of polyps, and location of polyps on the aforementioned DAR will be assessed. Furthermore, we will compare the incidence of complications and the differences in procedure time between the different endoscopic modes.

Inclusion Criteria:

• Patients aged 18 years or older.
• Patients who meet the indications for undergoing colonoscopy.

Exclusion Criteria:

• Patients younger than 18 years of age or those with contraindications precluding them from undergoing a colonoscopy.

(Contraindications for colonoscopy: patients with a recent history of myocardial infarction, pulmonary embolism, cerebrovascular infarction, severe unstable cardiovascular disease, acute abdominal inflammation combined with peritonitis, fulminant colitis, acute diverticulitis, colonic perforation, or toxic megacolon).

• Patients with familial hereditary colorectal cancer or colonic polyposis syndromes.
• Patients with inflammatory bowel disease (IBD).
• Subjects who are unable to complete the colonoscopy or those with poor bowel preparation.
• Subjects who are unable to confirm the date of their previous colonoscopy.