When a diagnosis of colon cancer is made, it is classified into different stages. This staging process provides a standardized way to describe the extent of the cancer, which helps doctors determine the most effective course of action. The stage is determined through various tests, including imaging and examination of tissue, and provides a roadmap for your medical team.
Defining the pT3 Stage in Colon Cancer
The staging of colon cancer is determined using the TNM system. This system evaluates three aspects of the cancer’s progression: the primary tumor (T), the involvement of nearby lymph nodes (N), and the presence of distant metastasis (M).
The “T” in the TNM system refers to the primary tumor and describes how far it has grown into the wall of the colon. The colon wall is composed of several layers, including the inner lining (mucosa), submucosa, a thick muscle layer (muscularis propria), and the outermost layers (subserosa and serosa). A pT3 diagnosis means the tumor has grown through the muscularis propria and has reached the subserosa or the fatty tissues surrounding the colon.
The “p” preceding T3 stands for “pathological,” signifying the staging was confirmed by microscopic examination of surgically removed tissue. This is more precise than clinical staging (cT), which is based on imaging tests before surgery. Pathological staging offers a definitive assessment of the tumor’s depth of invasion.
Determining the Overall Cancer Stage
To determine the overall cancer stage, the pT3 designation is combined with findings from the lymph nodes (N) and the presence of distant spread (M). The “N” component indicates if cancer has spread to nearby lymph nodes, and “M” indicates if it has metastasized to distant organs, such as the liver or lungs.
The combination of the T, N, and M values results in an overall stage, expressed as a number from 0 to IV. For instance, a cancer classified as pT3, with no spread to lymph nodes (N0) and no distant metastasis (M0), is categorized as Stage IIA. This stage indicates the cancer is locally advanced but has not yet spread to other parts of the body.
If the pT3 tumor has spread to nearby lymph nodes, the stage will be higher. A pT3 tumor with involvement of one to three nearby lymph nodes (N1) is classified as Stage IIIB. If the cancer has spread to four or more lymph nodes (N2), it is designated as Stage IIIC. The overall stage directly influences treatment recommendations and prognosis.
Standard Treatment Protocols
For a pT3 colon cancer diagnosis, the primary treatment is the surgical removal of the tumor and a section of the surrounding colon. Since a pT3 stage is determined pathologically, this surgery has already taken place. The focus then shifts to adjuvant therapy, which is additional treatment given after surgery to reduce the risk of recurrence.
The recommendation for adjuvant therapy depends on the overall stage. For Stage IIA (pT3 N0 M0) colon cancer, the use of adjuvant chemotherapy is decided on a case-by-case basis. It may be considered if there are high-risk features, such as the tumor causing a bowel obstruction or being poorly differentiated.
For Stage III colon cancer (any T, N1/N2, M0), adjuvant chemotherapy is the standard of care. The goal is to destroy microscopic cancer cells that may have escaped from the original tumor. Common chemotherapy regimens for Stage III colon cancer often include a combination of drugs, such as 5-fluorouracil (5-FU), leucovorin, and oxaliplatin, determined by your oncologist.
Prognosis and Survival Statistics
Prognosis statistics for colon cancer are often presented as 5-year relative survival rates, which compare people with the same type and stage of cancer to the general population. These are averages and cannot predict an individual’s outcome, as personal factors like age, health, and treatment response also play a role.
The 5-year relative survival rate for Stage IIA colon cancer, which includes pT3 N0 M0 tumors, is approximately 87%. This means that people with Stage IIA colon cancer are, on average, about 87% as likely as people who do not have that cancer to live for at least 5 years after diagnosis.
For Stage III colon cancer, survival rates vary by lymph node involvement. The 5-year relative survival rate for Stage IIIA is about 89%. For Stage IIIB, which can include pT3 tumors with limited lymph node spread, the rate is around 69%. For Stage IIIC, which involves more extensive lymph node involvement with a pT3 tumor, the rate is approximately 53%.
Post-Treatment Surveillance
After the completion of active treatment, a period of follow-up care and monitoring, known as surveillance, will begin. The purpose of surveillance is to watch for any signs of cancer recurrence.
A surveillance plan includes regular visits with your oncologist, every 3 to 6 months for the first few years and less frequently after that. During these visits, you will have a physical exam and discuss any symptoms. Blood tests to check for the carcinoembryonic antigen (CEA) tumor marker are also standard, as an elevated level can be an early sign of recurrence.
Imaging studies, such as CT scans of the chest, abdomen, and pelvis, are also recommended periodically to check for spread. A follow-up colonoscopy is recommended one year after surgery; the frequency of future procedures depends on the results. This regular monitoring helps ensure that any recurrence is detected and treated as early as possible.