The science behind the cancer cure

Subject : Science and Technology

Section: Biotechnology

Context:

In a medical trial, 12 patients in the United States were completely cured of rectal cancer without requiring any surgery or chemotherapy.
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.
The study was done by doctors from the Memorial Sloan Kettering Cancer Centre in New York, and its results have been published in the New England Journal of Medicine.

What are the findings?

The trial showed that immuno therapy alone – without any chemotherapy, radiotherapy, or surgery that have been staples of cancer treatment – could completely cure the patients with a particular kind of rectal cancer called ‘mismatch repair deficient’ cancer”.
All 12 patients had completed the treatment and were followed for six to 25 months after.
No cases of progression or recurrence had been reported during the follow-up. 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.
The anomalies in the DNA result in cancerous growths in patients with mismatch repair deficient cancers.
- For example, If you imagine the immune system to be a car, PD1 acts as the brakes for the T cells of the immune system. By giving the PD1 blockades, we release the brakes and allow the T cells to destroy the cancerous growth.
India has a couple of PD1 blockades available, although not the one used for this study.

If PD1 therapy was already in use, what’s new in the trial?

Earlier, this therapy was used post-surgery, but the study has shown that a surgery may not be required.
“Although the therapy is usually used for cancers that have metastasised (spread to locations other than where the cancer formed), it is now recommended for all mismatch repair deficient cancers as they result in quicker improvement and lesser toxicity as compared to traditional chemo and radiotherapy.
So far, this therapy was used after a patient undergoes surgery; it is used for 10 to 15 indications. This study shows that even the surgery was not needed in these patients.
In all tumours, they now look for mismatch repair deficiency to see whether immunotherapy can be used.
Eliminating other treatments can improve a patient’s quality of life by preserving fertility, sexual health, and bladder and bowel functions.