1. Imaging Staging of colorectal cancer Wei-Chou Chang ( 張維洲 ) Associate Processor Department of Radiology, Tri-Service General Hospital and National Defense Medical Center

2. General Information about colon cancer Colon cancer is a highly treatable and often curable disease when localized to the bowel. Surgery is the primary form of treatment and results in cure in approximately 50% of the patients. Risk Factors: Familial polyposis. Hereditary nonpolyposis colon cancer (HNPCC) or Lynch syndrome variants I and II. A personal history of ulcerative colitis or Crohn colitis. A personal history of colorectal cancer or adenomas. First-degree family history of colorectal cancer or adenomas. A personal history of ovarian, endometrial, or breast cancer.

3. Screening Because of the frequency of the disease, ability to identify high-risk groups, slow growth of primary lesions, better survival of patients with early-stage lesions, and relative simplicity and accuracy of screening tests, screening for colon cancer should be a part of routine care for all adults aged 50 years and older, especially for those with first-degree relatives with colorectal cancer.

4. Prognostic Factors The prognosis of patients with colon cancer is clearly related to the following: The degree of penetration of the tumor through the bowel wall. The presence or absence of nodal involvement. The presence or absence of distant metastases. These three characteristics form the basis for all staging systems developed for this disease. Other prognostic factors include the following: Bowel obstruction and bowel perforation are indicators of poor prognosis. Elevated pretreatment serum levels of carcinoembryonic antigen (CEA) have a negative prognostic significance.

5. Summary List (1) CT staging of colon cancer: TNM system (2) Morphologic Criteria to differentiate abnormal bowel wall in CT scan (3) Rectal cancer: review with emphasis on MR imaging

6. Staging Information Treatment decisions should be made with reference to the TNM classification rather than to the older Dukes or the Modified Astler-Coller classification schema. The American Joint Committee on Cancer (AJCC) and a National Cancer Institute–sponsored panel recommended that at least 12 lymph nodes be examined in patients with colon and rectal cancer to confirm the absence of nodal involvement by tumor. This recommendation takes into consideration that the number of lymph nodes examined is a reflection of the aggressiveness of lymphovascular mesenteric dissection at the time of surgical resection and the pathologic identification of nodes in the specimen. Retrospective studies demonstrated that the number of lymph nodes examined in colon and rectal surgery may be associated with patient outcome.

7. TNM staging classification of colon and rectal cancer

14. T Stage The presence of tumor extension beyond the muscularis propria is demonstrated by stranding of fat, spiculation, and spread to the tumor into the serosa and pericolic fat.

15. T1 tumor:invades submucosa CT findings: without any visible distortion of the bowel wall layers.--- usually means negative CT finding Pre-operative CT: Negative or Overstaging? Pathology: proven as T1 tumor But,

16. T2 tumor: invades muscularis propria CT findings: asymmetrical thickening projecting intraluminally with preservation of smooth muscle coat and clear adjacent pericolonic fat. CT findings: 1. colon bowel wall thickening 2. clear adjacent pericolonic fat But, Pathology: T3 lesion with 1 mm extramural invasion

17. T3 tumor: invades through subserosa CT findings: smooth or nodular extension of a discrete mass of tumor tissue beyond the contour of the bowel wall with extension into pericolic fat. An early T3 tumour. As nodular extension appears <5 mm beyond the contour of the bowel wall (arrows), it is a good prognosis tumour. Obvious T3 poor prognosis tumour with more than 5 mm spread (arrows), beyond the edge of the bowel wall. The tumour is also seen approaching the retroperitoneal fascia (arrowhead), which is the posterior resection margin.

18. Transverse CT colonographic image. In this patient, the rectal wall thickness (arrow) has a rounded advancing margin without spiculations in perirectal fat. Lesion was assessed as stage T3 tumor, which pathologic findings confirmed. Transverse CT colonographic image. In this patient, the rectal wall thickness has fine hyperattenuating spiculations (arrow) in perirectal fat. Lesion was assessed as stage T2 tumor, which pathologic findings confirmed. But one thing you should keep in mind: Pre-operative CT is not a pathological diagnosis

19. T4 lesion: invades to adjacent organ or perforation CT findings: (1) evidence of invasion of adjacent organ; (2) evidence of tumor perforation; (3) evidence of peritoneal infiltration. (1)(2)(3)

20. Nodal Stage Accurate detection of nodal status is difficult using CT. The most common criteria: any nodal mass larger than 1.0cm or a group of three or more nodes. Sensitivity: 66-83%; Specificity: 35-81%.

21. Transverse CT colonographic image. In this patient with a tumor (arrow) in the sigmoid colon. The coronal oblique MPR image showed a cluster of more than three small nodes (arrow), which led to staging of the tumor as N2; however, pathologic findings displayed a reactive pattern.

22. Extramural Venous Invasion independent prognostic indicator on 5-year survival rates at least two CT features are identified: (1) no definite extramural vascular invasion; (2) minimal stranding; (3) nodular spread into small vessels; (4) definite enhancing tumor spread along a large vein (3)(4)

23. Abnormal Bowel wall on CT 5 categories of attenuation patterns (1) white attenuation (2) gray attenuation (3) water halo sign (4) fat halo sign (5) black attenuation The spectrum of five attenuation patterns observed in bowel wall disease. * = use of intravenously administered contrast material is required to assess the pattern accurately

24. White Attenuation: indicating inflammatory process White attenuation: enhancement in acute ulcerative colitis. On an intravenous contrast- enhanced CT scan, the thickened wall of the rectosigmoid segment demonstrates uniform increased enhancement (straight black arrows) similar to the attenuation of the external iliac vein (curved arrow). Pericolonic vessels are dilated (white arrow).

25. Gray Attenuation: malignant tumor vs. diverticulitis Morphologic signs aiding diagnosis with the gray attenuation pattern. (a) Intravenous contrast-enhanced CT scan shows segmental annular thickening of the sigmoid colon (straight arrows) with sharp angular margins at either end (curved arrows) in adenocarcinoma. (b) Intravenous contrast-enhanced CT scan shows smooth, tapered margins (white arrows) at the edge of a mass in the sigmoid colon (black arrow) affected by diverticulitis. (a)(b)

26. Water Halo Sign: indicating ischemic or inflammatory process Water halo sign in ischemic colitis following administration of intravenous contrast material. Nonenhanced CT scan shows wall thickening of the distal transverse and proximal descending colon (straight arrows). The attenuation is largely of the gray attenuation pattern, although a partial halo sign is indistinctly evident (curved arrow). On the intravenous contrast-enhanced CT scan, a complete gray halo is clearly evident in the descending colon (straight arrows) and partially in the transverse colon (curved arrow).

27. Fat Halo Sign: Normal vs. Abnormal Normal fat halo sign (arrow). Note the sharply marginated interfaces between all layers and surrounding fat. Both muscularis propria and submucosal layers are very thin. Abnormal fat halo sign in Chronic disease. All three layers are slightly thickened for the degree of distention, and their interfaces are not sharply defined. Reaction in the contiguous mesentery (curved arrow) is compatible with creeping fat.

28. Pneumatosis in ischemic enteritis and colitis shows rounded mural gas attenuation collections (straight solid arrows), as well as the outer margin of the colonic wall (curved arrows) and lumen (open arrow). Black Attenuation: indicating pneumatosis (air density)

29. MR Staging for Rectal Cancer Endorectal US remains the most accurate staging tool for superficial rectal cancer, but is less suitable for advanced tumors Endorectal MR imaging can be as accurate as endorectal US for staging of superioficial tumors, and can also evaluate the advanced tumors Diagnostic challenge: T2 tumor (with perirectal fat spiculation or fibrosis) and borderline T3 tumors

30. Mesorectum consists of rectum (arrows) and surrounding mesorectal fat (*) with perirectal lymph nodes. It is enveloped by the thin mesorectal fascia (arrowheads). MRI anatomy of the mesorectum and the mesorectal fascia

31. Total mesorectal excision (TME) The surgical technique was standardized by the introduction of total mesorectal excision (TME). The mesorectum consists of the rectum and the surrounding mesorectal fat with the perirectal lymph nodes and is enveloped by a thin fascia known as the mesorectal fascia. In TME, the entire mesorectal compartment is removed, including its fascia; this minimizes the chance of tumor being left behind. With this surgical technique, the overall recurrence rate has been reported to be well below 10%, without the help of radiation therapy. TME+preoperative radiation therapy vs. TME without preoperative radiation therapy: reduces the local recurrence rate from 8.2% to 2.4% at 2 years. These results imply that even with a properly performed TME, patients with rectal cancer benefit from preoperative radiation therapy.

32. Schematic of circumferential resection margin (CRM) versus T stage The most powerful predictor for local recurrence is the shortest distance from tumor to mesorectal fascia (ie, the CRM) (double-headed arrows). The problem with the present T-staging system is that it does not discriminate between tumors with a wide CRM (T3 Δ ) and tumors with a close or involved resection margin (T3 * ). Although they have the same T stage, both groups have different risks for recurrence and require different treatment strategies. It would, therefore, be more important to be able to identify on images those bulky tumors that will have a close or involved resection margin than to predict the exact T stage of the tumor. T1 = T1-stage tumor, T2 = T2-stage tumor, T4 = T4-stage tumor, Ves = vesicula, Ves Sem. = vesicula seminalis.

33. T-staging vs. CRM Most staging failures with MR imaging occur in the differentiation of T2-stage and borderline T3-stage lesion, with overstaging as the main cause of errors. Overstaging is often caused by desmoplastic reactions. Postoperative combined chemotherapy and radiation therapy: the standard for patients with T3- and/or N1-stage tumors Shortcoming of present T-staging system: it does not discriminate between tumors with a wide CRM and tumors with a cloase or involved CRM.--both are classified as stage T3, but they have a different risk for local recurrence.

34. T2-stage rectal cancer overstaged at MR imaging as a T3-stage tumor in a 67-year-old woman. (a) MR image shows almost-circumferential rectal cancer (white arrow). Because of transmural stranding from tumor into perirectal fat (arrowheads), this tumor was staged T3. Mesorectal fascia (black arrows) is clearly depicted. CRM of more than 10 mm was predicted. (b) Corresponding microscopy section demonstrates tumor (black arrows) limited to the rectal wall (white arrow). Spiculations consisted of desmoplastic reaction alone (arrowheads), with no tumor cells.

35. T3-stage rectal cancer in a 70-year-old man. (a) MR image shows rectal tumor (black arrow) with transmural stranding (arrowheads) in mesorectal fat. Tumor stage was determined at MR imaging as T3. On the basis of MR images, a wide tumor-free CRM of more than 5 mm was predicted. Mesorectal fascia (white arrows) is clearly depicted. (b) Corresponding resection specimen shows T3-stage tumor (white arrows) has penetrated the rectal wall. Spiculations consist of desmoplastic reactions (arrowheads) containing tumor cells (black arrows). CRM was measured as 6 mm.

36. T3-stage rectal cancer with involved mesorectal resection plane in a 73-year-old man. (a) MR image shows bulky T3-stage tumor in anterior rectal wall (white arrows) extending to mesorectal fascia (black arrows). CRM was, therefore, predicted to be 0 mm. (b) Corresponding resection specimen confirms that tumor (thin arrows) has indeed invaded mesorectal fascia (thick arrows) and that the CRM is 0 mm. Patient had widespread metastatic disease and underwent palliative resection of the primary tumor.

37. (a) Transverse contrast-enhanced CT scan shows mass (arrows) in left lower pelvis of a 66-year-old man who underwent resection of rectal cancer 2 years previously. Diagnosis of local recurrence was made on the basis of involvement of left piriform muscle (arrowheads) and was confirmed at biopsy. (b) MR image in same patient clearly shows that tumor (black arrows) does not invade the left piriform muscle. An intact fat plane is still seen between tumoral and muscle tissues (white arrows). Multiplanar imaging capability and superior soft-tissue contrast resolution of MR allow more confident diagnosis of the exact extent of tumor invasion into surrounding structures. MRI is superior to CT for prediction of pelvic wall involvement from locally recurrent rectal cancer

38. MR images of rectal cancer with involved nodes in mesorectal fat. (a) Rectal tumor (arrows) with involved perirectal nodes (arrowheads) are all located within the mesorectum in a 69-year-old woman. (b) Rectal tumor (arrows) with involved perirectal nodes (arrowheads) are located within mesorectum in a 70-year-old man. Mesorectum is enveloped by mesorectal fascia. In TME, the entire mesorectum is removed, including fascia and nodes. (a)(b)

39. Rectal cancer with involved lateral node outside mesorectum. MR image shows enlarged, round, hyperintense lymph node (arrowheads) in left hypogastric region in a 54-year-old man with rectal cancer, suggestive of a metastatic node. This node is located outside the mesorectum, and with standard TME it would be left behind.

40. Recurrent rectal cancer in left hypogastric region in a 66-year-old man. MR image shows tumor mass (arrows) that is slightly hyperintense compared with hypointense muscle tissue in patient previously treated with TME for rectal cancer. No imaging had been performed before primary surgery. This MR finding is highly suggestive of local recurrence from nodal metastasis outside the mesorectal plane, in the left hypogastric region. The patient underwent curative resection of the recurrent tumor, and surgical and histologic findings confirmed the nodal origin of this recurrence.

41. Thank you for the attenuation!