Everyone treated remained cancer-free for up to two years, without the need for surgery or chemotherapy

Colorectal cancer, visualised here as a red mass in the colon, is the fourth most common cancer in the UK

A drug trial carried out in the US may hold new hope for treating cancer. Although conducted on a small number of patients, all of them were found to be entirely cancer free after a course of drug treatment.

The drugs in question are called PD-1 blockers, which inhibit the activity of a protein called PD-1 found on T-cells – the white blood cells that fight antigens.

PD-1 and another protein called PD-L1 prevent T-cells from attacking cancer cells, but restricting PD-1 cells’ activity leaves the T-cells free to fight the tumour.

A team of researchers at the Memorial Sloan Kettering Cancer Center in New York used a PD-1-blocking drug called dostarlimab to treat 14 patients with ‘mismatch repair-deficient’ (MMrD) stage two or stage three rectal cancers. The patients were given a dose of the drug every three weeks for six months, with a view to continuing treatment with chemoradiation and surgery afterwards, if required.

The researchers found, however, that no such further treatment was needed. Up to two years down the line, all 14 patients are still tumour-free. This offers hope that dostarlimab (or similar drugs) could help to reduce the number of colorectal cancer patients that require surgery each year.

“Surgery and radiation have permanent effects on fertility, sexual health, bowel and bladder function. The implications for quality of life are substantial, especially in those where standard treatment would impact childbearing potential,” said Dr Andrea Cercek, who co-led the research with Dr Luis Diaz, Jr. “As the incidence of rectal cancer is rising in young adults, this approach can have a major impact.”

“Two years down the line, all 14 patients are still completely tumour-free”

Each year, over 40,000 people in the UK are diagnosed with colorectal cancer. It affects 1 in 15 men and 1 in 18 women, according to the charity Bowel Cancer UK, making it the fourth most common form of cancer in Britain – and the second biggest killer.

Colorectal cancers can take many forms, but around 5 to 10 per cent of them can be characterised as MMrD.

This means there have been mutations in genes that are involved in ensuring the successful duplication of other genes, with the result that MMrD cells tend to feature mutations that can lead to cancer. If cancer does arise, MMrD tumours are generally less responsive to chemotherapy and radiation than other forms, leaving invasive surgery as the only treatment. In recent years, however, there has been some significant progress in the use of immunotherapy drugs to treat types of MMrD tumour in different parts of the body.

Writing in the New England Journal Of Medicine, another cancer researcher, Dr Hanna K Sanoff from the UNC Lineberger Comprehensive Cancer Center, welcomed the latest findings, saying that they were “very encouraging”, but also pointing out that they “need to be viewed with caution until the results can be replicated in a larger and more diverse population”.