In a medical trial, 12 patients in the US were completely cured of rectal cancer without requiring any surgery or chemotherapy.
The trial showed that immunotherapy alone – without any chemotherapy, radiotherapy, or surgeries that have been staples of cancer treatment.
It could completely cure the patients with a particular kind of rectal cancer called ‘mismatch repair deficient’ cancer”.
The trial used a monoclonal antibody called dostarlimab every three weeks for six months for the treatment of a particular kind of stage two or three rectal cancer.
All 12 patients had completed the treatment and were followed for six to 25 months after.
The response too was rapid, with symptoms resolving in 81% of the patients within nine weeks of starting the therapy.
What is this deficiency, and how was it cured?
‘Mismatch repair deficient’ cancer is most common among colorectal, gastrointestinal, and endometrial cancers.
Patients suffering from this condition lack the genes to correct typos in the DNA that occur naturally while cells make copies.
The immunotherapy belongs to a category called PD1 blockades that are now recommended for the treatment of such cancers rather than chemotherapy or radiotherapy.
PD1 is a type of protein that regulates certain functions of the immune system, including by suppressing T cell activity, and PD1 blockade therapy looks to release the T cells from this suppression.
Dostarlimab, an immunotherapy drug from GlaxoSmithKline, is a type of monoclonal antibody that blocks proteins called checkpoints which are made up of immune system cells, such as T cells, and some cancer cells.
These checkpoints help keep immune responses from acting too strong and may prevent T cells from killing cancer cells.
When these checkpoints are blocked, T cells are free to kill cancer cells more efficiently.
Examples of checkpoint proteins found on T cells or cancer cells include PD-1, PD-L1, CTLA-4 and B7-1. Some immune checkpoint inhibitors, called PD-1 inhibitors, are already used to treat various types of cancers.