Can immunotherapy treat bowel cancer?

What is immunotherapy, and can it be used to treat bowel cancer? Revered consultant medical oncologist Dr Aspasia Soultati, who treats patients in East Sussex, shares her expertise on the treatment which has proved effective in specific cases of bowel cancer.  

What is immunotherapy? 

Immunotherapy is a treatment that enables your immune system to fight cancer. Rather than offering you chemotherapy, which is toxic for cells in your body that reproduce quite quickly including cancer cells, immunotherapy does something completely different.

It unmasks those cancerous cells that have ways to evade and hide from the immune system and thus it enables the immune system to attack those cells and effectively kill them. Immunotherapy has a completely different toxicity side-effect profile from chemotherapy and has been already tested across various tumour sites, and in some cases with very impressive results.  

Can immunotherapy be used for bowel cancer? 

Immunotherapy has proven effective only for a specific cohort of patients with bowel cancer. Nowadays, when a patient is diagnosed with bowel cancer, the tissue that is resected from the bowel during a biopsy or a colectomy is sent for some specific DNA analysis. Among the markers that are checked is a specific DNA pathology called microsatellite instability (MSI).

It is a disorder where the DNA cannot repair itself, in basic terms, (deficient mismatch repair system). Microsatellite instability (MSI), is a hallmark of Lynch syndrome-associated cancers which is an inherited syndrome. MSI is also observed in about 15 % of sporadic (non-inherited) colorectal cancer. In patients who have MSI, studies have shown that there is a significant benefit from the use of immunotherapy. 

Which is more effective; chemotherapy or immunotherapy? 

In patients who are MSI normal, meaning they don’t have the microsatellite instability in their DNA in the tumour, chemotherapy is more effective, and immunotherapy cannot be offered. The response rates of first line chemotherapy in such patients range from 40 to 60 per cent, depending also on the rest of the molecular profile.  

In patients who have microsatellite instability, immunotherapy is the recommended first line treatment option. The response rates are very good and some patients have very prolonged responses. The choice of treatment is thus personalised and it depends on the specific analysis on the tissue from either the biopsy or bowel operation.   

How successful is immunotherapy for bowel cancer? 

Immunotherapy has proved to be very successful for patients with metastatic bowel cancer (bowel cancer that has spread to other organs) and microsatellite instability when offered as the first treatment option. In these patients, we have responses of 40-50% and in some cases responses for a prolonged period of time (83 per cent of patients having a response longer than two years, compared with 35% of patients receiving chemotherapy). 

How long can you live on immunotherapy? 

Usually, we continue immunotherapy for as long as the patient tolerates the treatment and as long as they are responding to the treatment. In cases of complete responses, we will consider continuing the treatment for two years and then stop, but continue to monitor the patient with regular scans.  

Does immunotherapy increase life expectancy? 

All palliative treatments that we use for metastatic bowel cancer, particularly the first-line treatment, have the potential to increase the patient’s life expectancy if the patient responds. For patients who have MSI, immunotherapy when used as the first-line treatment can achieve a prolongation of the patient’s progression-free survival (time that the cancer has not progressed) which is the time until the cancer progresses and needs further treatment. 

Dr Aspasia Soultati is an exceptionally skilled consultant medical oncologist in East Sussex. If you would like to book a consultation with her, visit her Top Doctors profile.