Colon Cancer Stage III

Stage III colon cancer has spread beyond the wall of the colon to nearby lymph nodes, but it has not reached distant organs. While this stage is more advanced than earlier stages, it remains curable for many people through a combination of surgery and chemotherapy.

Table of contents

• What is stage III colon cancer?
• Detailed breakdown of stage III
• Treatment approaches
• Outlook and survival

What is stage III colon cancer?

Stage III colon cancer means that the cancer has spread into nearby lymph nodes (small bean-shaped structures that help fight infection), but it has not reached other areas of the body^[1]. This is different from earlier stages where cancer is confined to the colon wall, and later stages where cancer has spread to distant organs^[2].

The cancer begins in the innermost lining of the colon, called the mucosa, and works its way outward through different layers of the colon wall^[3]. In stage III disease, the cancer has penetrated through various layers of the colon wall and has reached the lymph nodes near the colon.

Detailed breakdown of stage III

Stage III colon cancer is divided into three subcategories based on how far the cancer has spread through the colon wall and how many lymph nodes are affected^[1][2].

Stage IIIA

In stage IIIA, the cancer has spread through the innermost layer of the colon wall to the layer next to it (called the submucosa) or to the muscle layer of the colon wall. It has also spread into one to three nearby lymph nodes or into tissue near the lymph nodes^[1].

Alternatively, stage IIIA can also mean that the cancer has spread through the mucosa to the submucosa and has affected four to six nearby lymph nodes^[1][2].

Stage IIIB

Stage IIIB means the cancer has grown through the muscle layer of the colon wall to the outermost layer (called the serosa) or has spread through the outermost layer to the tissue that wraps around the colon. It has also spread to between one and three nearby lymph nodes or to areas of fat close to the lymph nodes^[1][2].

This stage can also include cancer that has grown into the muscle or outer lining of the bowel wall with four to six lymph nodes containing cancer, or cancer still in the inner or muscle layer but with seven or more nearby lymph nodes affected^[2].

Stage IIIC

Stage IIIC represents more extensive spread. The cancer has grown through the outer lining of the bowel wall into the tissue layer covering the organs in the abdomen with four to six lymph nodes containing cancer. It can also mean the cancer has spread to seven or more nearby lymph nodes, or has grown through the bowel wall into other nearby organs with at least one lymph node affected^[2].

Treatment approaches

Surgery as the first step

Surgery to remove the cancer is the primary treatment for stage III colon cancer^[2][6]. During surgery, the surgeon removes the section of the colon containing the cancer along with nearby lymph nodes. This procedure is essential for removing all visible cancer tissue.

Chemotherapy after surgery

Following surgery, doctors commonly recommend chemotherapy (powerful medicines that destroy cancer cells) for stage III colon cancer^[2][6]. This treatment is called adjuvant chemotherapy because it is given after the main treatment to reduce the risk of cancer coming back^[7].

Even when surgery successfully removes all visible cancer, tiny amounts of cancer cells may have spread beyond the colon. These invisible cells, called micrometastases, cannot be detected with any currently available tests^[7]. Chemotherapy targets these hidden cancer cells to prevent the cancer from returning.

The standard chemotherapy approach combines a drug called 5-fluorouracil (5-FU) with leucovorin (LV). More recently, doctors have found that adding a drug called oxaliplatin (brand name Eloxatin) to this combination improves outcomes^[7]. This three-drug combination, abbreviated as FOLFOX or FLOX depending on how it is given, has become a standard treatment option.

Research shows that adding oxaliplatin increases the number of patients who remain cancer-free after three years by 5 to 7 percent^[7]. Another medication called capecitabine (brand name Xeloda) offers an oral pill form of chemotherapy that works as well as traditional intravenous 5-FU with fewer side effects^[7].

Duration of treatment

The typical duration of chemotherapy for stage III colon cancer is three to six months^[14]. Chemotherapy usually starts within eight weeks after surgery^[14]. Treatment sessions may require several hours a day, multiple days per week, depending on the specific regimen chosen.

Chemotherapy before surgery

In some cases, doctors may suggest chemotherapy before surgery^[2]. This approach, called neoadjuvant chemotherapy, can shrink the cancer to make it easier to remove during surgery. Research into this approach for colon cancer shows promise, though more long-term data is still needed^[12].

Outlook and survival

Despite the challenges of stage III colon cancer, many patients can be cured with proper treatment. Depending on the specific features of the cancer, 40 to 50 percent of patients are cured with surgery alone^[7]. When chemotherapy is added after surgery, cure rates improve significantly.

Research shows that adjuvant chemotherapy with combination treatments results in five-year overall survival rates of 73 to 84 percent in clinical trial populations^[12]. Five-year disease-free survival (meaning no return of cancer) ranges from 66 to 70 percent with modern treatment approaches^[12].

Studies have demonstrated that three-year disease-free survival rates reach 72 to 76 percent when patients receive 5-FU/LV plus oxaliplatin, compared with 65 to 72 percent with 5-FU/LV alone^[7].

However, it is important to understand that even with complete surgical removal of cancer, about half of patients with stage III colon cancer experience recurrence of their disease^[7]. This happens because of micrometastases that cannot be seen or removed during surgery. This is why additional treatment with chemotherapy is so important for improving outcomes.

Researchers continue working to better identify which patients will benefit most from different treatment approaches and to develop new therapies that can further improve survival rates for stage III colon cancer^[11].