Immunotherapy For Colorectal Cancer: All You Need To Know

Immunotherapy has shown remarkable results for a subset of colorectal cancer patients. Read to know who is the ideal candidate for immunotherapy.

Colorectal cancer is the most common gastrointestinal cancer, and sadly its prevalence is increasing in younger age groups. There is an unmet need for new treatment options for this type of cancer, where surgery, chemotherapy and targeted therapy are the only available treatment options for many patients. With increasing survival rates, less side effects and demand for better quality of life, the role of newer drugs especially immunotherapy in the treatment of colorectal cancer is being extensively evaluated in many countries.

To understand how immunotherapy for colorectal cancer works and who can undertake the treatment, we connected with Dr. G. Vamshi, Krishna Reddy, Director-Oncology Services, Consultant Medical Oncologist & Hemato Oncologist, Yashoda hospitals Hyderabad. Here’s what he says about this cancer treatment method.

What is immunotherapy?

Immunotherapy involves use of injections to help the person’s own immune system to better recognize and destroy the cancer cells. The recent reports of an immunotherapy drug, dostarlimab used in a small group of rectal cancer patients with mismatch protein deficiency giving 100 per cent complete response with avoidance of chemotherapy, radiation and surgery has given hope for many.

How effective is immunotherapy for colorectal cancer?

Immunotherapy has shown remarkable results for a subset of colorectal cancer patients, precisely those with mismatch-repair-deficient mutations or microsatellite instability in their tumors. This subset of patients who benefit are only 3-6 per cent and they need to be tested positive for this specific biomarker in their tumor.

Immunotherapy has shown excellent tolerability, durable response, and, in some cases, even cure. The field of immunotherapy is growing exponentially, and preliminary studies are showing promising results.

With the generally tolerable side-effect profile of immunotherapy, and the success in a multitude of different malignancies, immunotherapy has become an attractive option compared with conventional chemotherapy for colorectal cancer.

Who is the ideal candidate for immunotherapy?

Currently the role of immunotherapy in colorectal cancer is limited to a small subset of patients expressing microsatellite instability (MSI-H and dMMR) tumors in a chemotherapy refractory setting. Multiple studies are investigating the potential role of immunotherapy at all stages of colorectal cancer and using combination modalities to enhance immune response regardless of microsatellite gene status.

As of today, only those patients with advanced stage colorectal cancer who are tested positive for microsatellite instability have the benefit with immunotherapy. Though the side effects are less, cost is a concern for many and is still out of reach for the majority.

Final word

To conclude, immunotherapy in colorectal cancer is useful only in a small subset (3-6 per cent) of advanced stage patients and they need to be tested positive for microsatellite instability (MSI-High).

Surgery is still the standard treatment for early-stage colorectal cancer, and it is followed by adjuvant chemotherapy if required based on the stage. Advanced stage colorectal cancer is treated with chemotherapy and targeted therapy.

Genetic counselling and testing are suggested for those patients having microsatellite instability (MSI-High) to rule out hereditary cancer susceptibility genes.