Staging is the inclusion of cancer in a stage of development previously defined. The purpose is to predict the probability of cure after the cancer removal, thus contributing to determine the need of additional treatments.

Considering that, unlike other tumors, the size of colorectal cancer has little influence on the probability of cure, the definition of the stages of development is based on:

  • The progression of the tumor through the intestinal wall (is it confined to the wall? has it already passed through the wall?);
  •  The dissemination of the tumor to local lymphatic ganglia;
  • The dissemination of the tumor to more distant organs or tissues.

Considering these aspects, tumors are classified as stage I, II, III or IV.

Usually, colorectal cancer relapses occur in the first two years after surgery, and almost all cases of relapse (95%) happen within five years. The best probability of cure or the best prognosis are associated with stage I cancers, where 90% of patients survive for more than five years after surgery.

Staging may require several exams, including blood tests to search for specific compounds, colonoscopy, endorectal ecography, thoracic radiography, computerized tomography, positron emission tomography (PET and PET-CT), among others.

The microscopic appearance of tumor cells is also important to determine treatment. This appearance, designated “differentiation”, allows to generically classify tumors as well differentiated, moderately differentiated or poorly differentiated. Patients with well differentiated tumors have a better prognosis than those with poorly differentiated tumors.

Thus, staging and differentiation help the doctor to decide if radiotherapy and/or chemotherapy is necessary as complementary treatment to surgery.