Is stage 4 colon cancer or rectal cancer curable?

Colorectal cancer originates in the colon and rectum (large intestine). It is the third most common cancer worldwide. It is among the top ten cancers in India and its incidence is increasing.

Cancers tend to spread. When cancer spreads from its primary organ of origin to distant parts of the body, it is called metastasis (secondary). Metastasis can be present during the initial detection of cancer or can reappear later (recurrence) after the treatment of the primary cancer. Colorectal cancer often spreads to the liver, lungs, peritoneum, bones and distant lymph nodes.

When the cancer has spread to distant organs, it is referred to as stage 4 cancer.

For many types of cancer, stage 4 is considered incurable. With modern chemotherapy, Patients diagnosed with stage 4 colorectal cancer survive for 2-3 years. However, Some stage 4 patients have spread limited to a few spots of cancer in the lung, liver and peritoneum. If all these spots can be removed, then surgery has the potential to cure the disease and prolong life.

The liver is a common site of metastasis in colorectal cancer. Between one-third to half of all colorectal cancer patients will either present with or eventually develop liver metastases. These may be synchronous (detected at the same time as colorectal cancer) or metachronous (developing later).

The peritoneum is a membrane that lines inside of your abdomen. It also covers many of our abdominal organs. The peritoneum is another common site of metastasis from colorectal cancer. The peritoneal disease is often less responsive to chemotherapy and targeted therapy because of poor delivery of these drugs to the peritoneum.

Other common sites of metastasis include the lung, distant lymph nodes and bone.

Not all stage 4 patients can be treated with curative intent. Approximately one-third stage 4 patients have a disease which can be removed. This sometimes requires multiple steps and a combination of multiple treatment modalities.

Cytoreductive surgery (CRS) and Hyperthermic intraperitoneal chemotherapy (HIPEC)

Cancer that has limited spread to the peritoneum is treated with Cytoreductive surgery (CRS) and Hyperthermic intraperitoneal chemotherapy (HIPEC). During cytoreductive surgery, all visible tumours are surgically removed. This surgery is often combined with HIPEC, which involves delivering heated chemotherapy drugs directly to the abdomen. This allows for higher doses of chemotherapy with improved effectiveness because of heating. It destroys the microscopic cancer cells that can remain in the abdomen after surgery. This helps improve the chances of survival and reduce the likelihood of recurrence.

Liver resection for colorectal cancer liver metastasis

When the liver has limited spread from colorectal cancer, surgery can cure or prolong survival. The part of the liver with cancer can be surgically removed in a procedure called metastasectomy. Sometimes, it is necessary to remove a larger part of the liver in a procedure called hepatectomy. The remaining liver grows over a few weeks. Sometimes liver resection can be combined with ablation and can also be done in multiple stages to completely clear the disease.

Ablation for colorectal cancer liver metastasis

Ablation destroys cancer cells using extreme heat, cold or chemicals. It works best for small tumours in the liver that are less than 2 cm. This procedure may involve Radiofrequency ablation (RFA), Microwave ablation, Cryoablation or cryotherapy, or Percutaneous ethanol injection (PEI). A probe is inserted into the tumour, guided by ultrasound or CT scan and the tumour is ablated.

Lung resection

Pulmonary (lung) resection is a surgical procedure to remove the part of the lung, which has cancer.

Stereotactic Body Radiation Therapy (SBRT)

The procedure uses many precisely focused radiation beams to treat tumours. It can be used to destroy some of the cancer cells not amenable to surgery.

Perioperative, neoadjuvant and adjuvant systemic treatment

Chemotherapy - Besides surgery, many of these patients are administered chemotherapy. Sometimes a few cycles of chemotherapy are given before surgery and the rest after surgery. Otherwise, the chemotherapy is administered after surgery. The choice depends on where the spots are, how many there are, how soon they have come and how big they are.

Chemotherapy can help shrink the spots and kill hidden cells. Progression of tumour on chemotherapy and increased risk of surgery following chemotherapy is a concern.

Targeted and immunotherapy - Some patients will also receive targeted therapy or immunotherapy. Targeted therapies are antibodies or drugs that inhibit specific proteins that are required for cancer cell growth. They attack cancer cells without harming normal cells. Targeted therapy is added to chemotherapy when the liver metastases are deemed unresectable and the aim is to shrink it and make it resectable.

There is an emerging role of immunotherapy in a subset of patients. These are patients who have deficient DNA mismatch repair (dMMR) genes or microsatellite instability-high (MSI-H).

The current 5-year survival rate for colorectal cancer metastases after surgery is around 40-60%.

Early detection and appropriate treatment can save lives.