Stage 3 is further divided into 3A, 3B, and 3C, with the distinctions based on how far the cancer has spread and the number of lymph nodes involved. Colon tumors in stage 3 have migrated to adjacent lymph nodes but have not yet spread to distant organs.

Stage 3A

  • T1: The malignancy has progressed through the mucosa of the colon wall and into the submucosa.
  • N2a: The malignancy has progressed to four to six lymph nodes in the area.
  • MO: The cancer hasn't spread to other parts of the body or to other organs.

Or

  • T1 or T2:  The malignancy has spread from the mucosa to the submucosa (T1) or from the muscularis propria to the submucosa (T2)
  • N1 or N1c: The cancer has spread to 1 to 3 lymph nodes (N1a or N1b) or has spread to the subserosa, or tissues adjacent to the colon but not to the lymph nodes (N1c).
  • M0: The cancer hasn't affected other parts of the body or  other organs.

Stage 3B

  • T1 or T2: The malignancy has gone through the mucosa and into the submucosa of the colon (T1), and it may have spread into the muscularis propria (T2)
  • N2b: The malignancy has progressed to seven or more lymph nodes in the area.
  • M0: There is no evidence that the malignancy has spread to other organs or sites.

Or

  • T2–T3: The malignancy has spread from the submucosa to the muscularis propria (T2) or the sub serosa (T3)
  • N2a: The malignancy has progressed to four to six lymph nodes in the area.
  • M0: There is no evidence that the malignancy has spread to other organs or sites.

Or

  • T3-T4a

Subserosa(T3) or serosa involvement without adhesion to adjacent tissues (T4a)

  • N1/N1C

The cancer has spread to 1 to 3 lymph nodes (N1a or N1b) or has spread to the subserosa, or tissues adjacent to the colon but not to the lymph nodes (N1c).

  • M0 : The malignancy has not affected other parts of the body

Stage 3C

  • T3 or T4a: The cancer has spread to the colon's outer layers (T3) or the visceral peritoneum (T4a).
  • N2b: The malignancy has progressed to seven more lymph nodes in the area.
  • M0: There is no evidence that the malignancy has spread to other organs or sites.

Or

  • T4b: The cancer has spread through the colon or rectum wall and has attached itself to or expanded into surrounding tissues.
  • N1 and/or N2: The cancer has migrated to at least one neighbouring lymph node, as well as the fat tissues around the lymph nodes (N1 or N2).
  • M0: It has not spread to other locations.

Or

  • T4a : Cancer has spread to the serosa, however it is not attached to the surrounding tissues.
  • N2a: The malignancy has progressed to four to six lymph nodes in the area.
  • M0: It has not spread to other locations.

Treatment

  • For those with stage 3 colon cancer, a partial colectomy is the procedure of choice. A partial colectomy is a technique that involves removing a portion of the colon that has been damaged by cancer. Adjuvant chemotherapy is the standard therapeutic choice after surgery.
  • For patients who are not in good enough health to undergo surgery, radiation therapy or chemotherapy may be employed as a treatment option. After surgery, radiation therapy may be used to prevent cancer recurrence. It may also be used if the tumor has expanded into or attached itself to adjacent tissue. It may also be used if the cancer has not been completely eliminated.
  • After surgery, chemotherapy is given to lower the risk of recurrence. Chemotherapy is given for 6 months and begins 4 to 6 weeks following surgery.

Stage 3 colon cancer prognosis

The five-year relative survival rate for those with stage 3A colon cancer is 90%. People with stage 3B colon cancer have a 72 percent five-year relative survival rate, whereas those with stage 3C have a 53 percent five-year relative survival rate.