Bowel cancer cells under a microscope

Bowel cancer cells under a microscope.

The Scottish Medicines Consortium (SMC) has approved the immunotherapy drug pembrolizumab (Keytruda) for some adults with bowel cancer that’s spread to other parts of the body.

Pembrolizumab will be made available to people with bowel cancers that are unable to repair DNA damage, which means these types of tumours have a lot more errors (mutations) in their DNA.

It’s the first immunotherapy, and the first chemotherapy-free option for this group of bowel cancer patients.

It’s great news that pembrolizumab has been approved to treat metastatic colorectal cancer in Scotland. It is a landmark decision for patients and their families, as it’s the first drug of its kind to be made available for this type of cancer.

David Ferguson, public affairs manager for Cancer Research UK in Scotland

A ‘landmark’ decision offers new hope

Around 4 in 100 metastatic bowel cancers have a lot more DNA mutations than others, as they’re unable to repair any mistakes that are made in their DNA. These cancers are said to have high ‘microsatellite instability’ (MSI) or ‘mismatch repair (MMR) deficiency’, which can make them more aggressive.

Chemotherapy-based treatments are currently offered for these cancers, but they can have high toxicity and can cause debilitating side effects. Pembrolizumab could offer new hope to these patients.

“This drug will now be offered to patients who have a specific type of colorectal cancer where the DNA repair mechanism is damaged. Prior to this approval, these patients had no options for treatment outside of chemotherapy. Today’s decision will make a real difference to their lives, offering them the chance of more precious time with their loved ones.”

Why does immunotherapy work better for these patients?

Immunotherapies harness the body’s immune system to fight cancer. Researchers have found that bowel cancer tumours with high MSI or MMR deficiency have a lot of immune cells within them, but the cancer stops them from working. Pembrolizumab blocks the PD1 pathway, which may help the body’s immune system fight the cancer cells.

“Pembrolizumab provides a more targeted approach to treating cancer, by helping the immune system to attack tumours. Studies have shown that it slows down the time that it takes for many different types of cancer to grow and spread around the body,” says Ferguson.

A less toxic option

In a phase 3 clinical trial, patients who were given pembrolizumab lived without their cancer growing for longer – from an average of 8.2 months for patients on one of the current 6 chemotherapy options, to 16.5 months for patients taking pembrolizumab.

Results from a patient group submitted by Bowel Cancer UK found that pembrolizumab tends to mean fewer hospital visits and shorter treatment cycles. The side effects are also often less toxic than current chemotherapy options.

This new treatment option was made available to people with bowel cancer patients in England on the NHS in May this year.

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