Introduction to the Large Bowel
Colorectal cancer is the third most common cancer in the world. In the USA, 150,000 new cases are diagnosed annually, whereas in Europe the respective incidence is 400,000. The ratio of colonic to rectal cancer is 2:1. Colorectal cancer is more common in males than females. Colonoscopy with biopsy is the most often used method for diagnosis. Cross-sectional imaging follows colonoscopy for staging purposes in an effort to detect metastatic disease. CT and MRI are not recommended for detection of the colonic primary lesion, however, as always used for identification of metastatic lesions through the body. However, PET-CT scan is extremely useful for whole-body imaging especially in restaging where lung or liver metastasectomy is the preferred mode of treatment. Specifically for rectal cancer, staging is of major importance for treatment planning. Endorectal ultrasound (ERUS) and MRI visualize the extrenth of the tumor as well as the circumferential resection margin which is significant for total mesorectal excision. The ideal surveillance strategy for colorectal cancer has not been defined. NCCN guidelines recommend CT scans of the upper and lower abdomen as well as the chest every year for 5 years. Colonoscopy is recommended 1 year following surgery and then at 3 years and then every 5 years.
KeywordsColorectal cancer Staging Surveillance PET-CT scan Endorectal ultrasound
Colorectal cancer is the third most common cancer in the world. In the USA, 150,000 new cases are diagnosed annually, whereas in Europe the respective incidence is 400,000 . The ratio of colonic to rectal cancer is 2:1. Colorectal cancer is more common in males than females .
Colorectal cancer is highly a preventable disease. Screening and removal of premalignant polyps have contributed to the decline of the incidence during the past three decades.
Early diagnosis is extremely important which results in a 5-year survival of 90%. The 5-year survival of patients with this disease has improved significantly during the past 10 years due to the improved surgical techniques and novel molecular agents.
However, the contribution of new imaging technology is of paramount importance. The early detection of polyps, the accurate staging and restaging, the assessment of response to treatment, and the surveillance are issues directly related to imaging techniques. In particular, imaging contribution for residual liver metastatic lesions and evaluation of response following radio-chemotherapy for rectal cancer are important information to the oncologist for decision-making process. CT, CT colonography, MRI, PET-CT, and endorectal ultrasound are useful and necessary techniques which make the radiologist’s role great and his cooperation with the oncologist mandatory.
- 1.World Health Organization. Global burden of disease. http://www.who.int/entity/healthinfo/global_burden_disease