What is Colon Cancer?

The colon is the part of the large intestine that extends up to the last 12 cm, called the rectum. It is divided into 7 sections: cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colon. The rectosigmoid junction refers to the area where the sigmoid colon connects to the rectum, not a part of the colon itself. Cancers developing in this region are referred to as colon cancer.

Symptoms of Colon Cancer

The initial symptoms of patients vary depending on the location of the tumor. Tumors on the right side may cause complaints such as anemia and weakness. Tumors on the left side, on the other hand, may lead to changes in bowel movements such as constipation or diarrhea, as well as symptoms like rectal bleeding, abdominal pain, and bloating. Additionally, colon cancer can be detected through screening methods such as colonoscopy, or through other examinations like CT scans, MRIs or PET-CT scans.

Diagnosis of Colon Cancer

The primary diagnostic method for colon cancer is colonoscopic examination. A biopsy is taken from the tumor tissue during colonoscopy to provide a tissue sample for pathological examination. This helps determine whether the tumor is in its early stages and if there are lesions in other parts of the colon or if there is a familial polyposis syndrome.

Before planning the treatment for colon cancer, staging should be performed. Staging includes:

• Upper abdomen (abdominal) CT scan
• Lower abdomen (abdominal) CT scan
• Thoracic (lung) CT scan
• Upper abdomen MRI (if there is suspicion of liver metastasis)

PET-CT is not routinely recommended for staging colon cancer but is suggested for evaluating patients with suspected metastasis. Although not used in staging, blood values coded as CEA and Ca 19-9 are recommended to be tested at the time of initial diagnosis to predict the course of the disease and monitor recurrence after treatment.

Colon Cancer Treatment

The treatment of colon cancer is planned according to the stage of the tumor. Below, you can see the main treatment options according to the stages:

• Stage 1,
  • Colonoscopic intervention (endoscopic submucosal dissection – ESD),
  • Colorectal surgery (open, laparoscopic, robotic).
• Stages 2 & 3,
  • Colorectal surgery (open, laparoscopic, robotic)
• Stage 4,
  • (Distant organ metastasis) Chemotherapy

Additional treatments may be considered depending on the region where metastasis has occurred. For patients with only lung or liver metastasis that can be completely removed, simultaneous or different-time planning of colon surgery and removal of metastases is considered.

In patients with peritoneal metastasis, after chemotherapy or immediately following the diagnosis, HIPEC (hyperthermic intraperitoneal chemotherapy) can be applied together with cytoreductive surgery. Surgical interventions can be planned even in cases of simultaneous metastasis in multiple regions.

In all stages, the treatment plan is decided in a multidisciplinary oncology council involving colorectal surgeons, medical oncologists, pathologists, radiologists, and other relevant branches. Taking into account the patient’s and tumor’s characteristics, decisions are made based on current scientific data.

Colon Cancer Surgery

The fundamental rule in colon cancer surgery is to cut the intestine at least 10 cm away from the tumor and simultaneously ligate the main vessel(s) supplying the tumor. Depending on the areas supplied by the ligated vessels, in some cases, it may be necessary to go up to 20-30 cm away from the tumor.

In recent years, an embryological structure surrounding the large intestine, enclosing the tumor and the surrounding lymph nodes like a sheath, has been identified. Accordingly, surgery with a complete mesocolic excision, which prevents the spread of the tumor, is recommended.

During surgery, it is essential to remove the tumor without fragmentation and without causing damage to surrounding tissues and organs. Depending on the tumor’s location, organs such as the duodenum, stomach, pancreas, spleen, kidneys, upper urinary tract, vessels and nerves supplying the intestines, gallbladder, and liver need to be preserved unless the tumor has progressed. If the tumor extends towards any of these structures, the affected organ should be removed as a whole along with the primary mass.

Adhering to all these surgical principles, colon cancer surgery can be performed through traditional (open) methods, laparoscopic, or robotic approaches. Scientific data show that laparoscopic surgery provides cancer surgery effectiveness comparable to open surgery while offering several advantages. The higher cost of robotic surgery has not shown a significant superiority over laparoscopic surgery. Therefore, in current colorectal surgical practice, laparoscopic surgery is primarily recommended for colon cancer.