What are the treatments for colon cancer ?
Personalized treatment
The treatment of colorectal cancer is increasingly personalized: for each patient, it depends on various elements collected during the diagnosis and staging of the disease: the nature and grade of the cancer cells, any mutations and the MSI status of the cancer cells, as well as the location and stage of the disease.
Once colorectal cancer has been diagnosed in a patient, the treating physician or gastroenterologist, often the one who made the diagnosis, will refer the patient to an oncologist specialized in treating these cancers. The treatment decision for each patient will not be made by the oncologist alone because every patient is unique.
In practice, each patient's case will be discussed during a Multidisciplinary Team Meeting (MDT) or Tumor Board. This meeting involves at least an oncologist, a radiotherapist, and a digestive surgeon. An anatomopathologist or molecular biologist may also be present to provide their opinion on specific cases.
Once a treatment plan has been decided upon during the MDT, the physician initially managing the disease (oncologist, surgeon, or radiotherapist) will explain in detail the treatment plan during a dedicated consultation called an announcement consultation.
"Treatment plan" is indeed an appropriate term as the patient will be offered a sometimes-lengthy journey marked by several stages. During these stages, one or more of the five available cancer treatments will be utilized: two of these treatments are local/regional—surgery or radiotherapy, and three are systemic treatments—chemotherapy, targeted therapy, or immunotherapy.
Surgery
The goal of surgery for colorectal cancers is to remove the primary tumor and nearby lymph nodes. The extent of surgery can vary from resection of a small part of the colon or rectum to more extensive segments. Surgery may also be used to remove one or more metastases, particularly in the liver.
Surgical procedures are performed either traditionally, with an incision in the abdomen, or laparoscopically.
Expert perspective
This technique requires only small incisions through which a small camera is inserted into the abdomen to visualize the area for surgery, along with small instruments to remove tumor areas. Laparoscopy is becoming more common because it is as effective as traditional techniques but offers the advantage of smaller scars, reduced postoperative recovery, and shorter hospital stays.
Radiotherapy
For colorectal cancers, radiotherapy is primarily used to treat rectal cancers.
Radiotherapy involves using radiation to destroy cancer cells or prevent them from multiplying. The schedule and duration of treatment are determined by a radiation oncologist. Typically, it involves 5 sessions per week for 5 weeks. Each session lasts about 15 minutes, with the actual irradiation lasting only a minute. Radiotherapy is invisible and painless.
Chemotherapy
Chemotherapy for colorectal cancers may be administered before surgical treatment to shrink the tumor prior to surgery. This treatment, known as "neoadjuvant" chemotherapy, can be given as chemotherapy alone or combined with radiotherapy, particularly for neoadjuvant treatment of rectal cancers. Chemotherapy is also administered after surgical intervention.
This post-surgical treatment, referred to as "adjuvant" chemotherapy, aims to eliminate cells that may have spread distantly from the primary tumor and to prevent recurrence. Chemotherapy can also be used to treat colorectal cancers that are inoperable and/or metastatic.
Expert perspective
The goal of chemotherapy is to kill rapidly dividing cells , such as cancer cells. However, some normal cells in the body also divide rapidly, including blood cells, cells in hair follicles (which produce hair), and cells lining the gastrointestinal tract. Damage to these normal cells can cause side effects from certain chemotherapy treatments.
Before chemotherapy, blood tests are performed to ensure that levels of red blood cells (responsible for oxygen transport to tissues), white blood cells (immune defenses), and platelets (blood clotting) are normal. During treatment, these levels are monitored regularly. It is also important to check for infections, including dental infections.
Chemotherapy often involves a combination of several medications administered via intravenous infusion lasting approximately 3 hours. To facilitate these infusions, patients often have a port implanted beneath the skin near the collarbone. This port connects to a large vein via a thin, flexible tube (catheter), allowing medications to be injected directly into the port. This method is more comfortable for the patient than repeated infusions through a peripheral vein.
One of the most commonly used chemotherapy protocols is called FOLFOX, which combines the platinum salt oxaliplatin with folinic acid and fluorouracil. Chemotherapy protocols for colorectal cancers evolve annually, with significantly improving outcomes. Recent advancements include combinations of chemotherapy with targeted therapies.
Targeted therapies
Expert perspective
As their name suggests, targeted therapies specifically target molecules involved in the transformation of normal cells into cancerous cells or in the development of malignant tumors. Unlike chemotherapy drugs, which broadly oppose the proliferation of cancer cells, targeted therapy medications aim at the underlying mechanisms of cellular transformation leading to cancer.
For colorectal cancers, two different molecules are targeted. The first is VEGF, a molecule involved in blood vessel growth. By blocking VEGF, targeted therapy prevents the tumor from being supplied with blood vessels, thereby halting its growth. The second molecule is the EGFR receptor (EGFR), a growth factor implicated in the development of colorectal cancers. However, an anti-EGFR targeted therapy can only be used in the absence of mutations in a gene called KRAS. Mutations in this gene are responsible for resistance to anti-EGFR targeted therapy.
Therefore, it is necessary to screen for mutations in this gene before using this type of targeted therapy.
Recently, immunotherapy has emerged as the fifth weapon against cancers and is now used for treating certain colorectal cancers.
Immunotherapy
Immunotherapy treatment using checkpoint inhibitors represents a significant breakthrough in the treatment of cancers, including kidney cancers.
These treatments are based on three key discoveries :
- The first, the identification of specific molecules known as checkpoints that can accelerate or slow down the immune system's function.
- The second, the discovery that cancer cells can exploit checkpoints that inhibit the immune system to evade its detection. They particularly use a checkpoint called CTLA-4 to slow down the immune system. This checkpoint is located on specialized white blood cells called helper T lymphocytes, which are crucial for stimulating an immune response. CTLA-4 slows down the action of these lymphocytes. Another checkpoint is PD-L1, which is present on the surface of cancer cells. This molecule binds to another molecule called PD-1, found on the surface of other white blood cells, cytotoxic T lymphocytes, which are responsible for eliminating cancer cells. The binding of PD-L1 to PD-1 prevents lymphocytes from performing their role and eliminating tumor cells.
- The third discovery is that medications blocking the checkpoints CTLA-4, PD-1, or PD-L1 can re-stimulate the immune system to eliminate tumor cells. These medications are immunotherapies because they do not directly eliminate cancer cells as chemotherapy does, but rather stimulate the immune system to eliminate cancer cells.
These immunotherapies are often more effective if cancer cells have numerous PD-L1 molecules on their surface.
Expert perspective
Management in case of metastatic disease
Therapeutic strategies for metastatic cancers are more complex .
They may involve combining surgery for the primary tumor and metastases with chemotherapy. However, most often treatment relies primarily on medical therapies including intravenous or oral chemotherapies, targeted therapies tailored to the genetic characteristics of the tumor. Finally, a small subgroup of patients may benefit from anti-PD-1 immunotherapy (checkpoint inhibitor) with often remarkable results. These are tumors with microsatellite instability (as mentioned previously).
Such cases are relatively rare: only 4 to 5% of metastatic colon cancers exhibit microsatellite instability. Nearly 50% of these patients respond to immunotherapy with long remissions that can sometimes be considered as cures. Currently, numerous combinations including immunotherapy are under study, and it is reasonable to expect that these combinations will increase the number of patients who can benefit from them.
Clinical trials
Clinical trials can be an additional treatment opportunity.
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Article updated on Nov 14, 2024
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