Dostarlimab trial: ‘Light at the end of a tunnel’

It could well go down in the history of cancer treatment as a day that generated much hope in patients, and their doctors.

On June 5, a paper published in the New England Journal of Medicine said that 12 patients with mismatch repair–deficient (MMrD) colorectal cancer who were treated with dostarlimab (an immunotherapy drug) showed no evidence of the tumour after at least six months of follow-up.

For many who have grappled with cancer in their life, this development signals light at the end of a long and dark tunnel.

And while the medical community shares the overall optimism on the findings, cancer specialists are treading with caution and holding back from calling it “a miracle cure”, until there is more data, on more people, and for a longer duration.

Dr CS Pramesh, Director, Tata Memorial Hospital, the country’s largest cancer hospital, finds the initial results exciting. “It is by no means a trivial advance in time,” he says, hopeful that more groups of patients see similar breakthrough results.

The basis of medical research is that a drug is first given in a smaller group of patients for proof-of-concept and, when it shows promise, the trial is expanded to more patients to demonstrate efficacy, he explains.

The present exuberance in several quarters is “premature”, he says, as patients need to be monitored for three to five years more. And, the end point of the study should be on improved survival rates, he said, adding that tumours do tend to respond to treatment.

India studies

The early results should not be a reason to cut short trials, says Pramesh, calling for multi-centre Phase III trials to be brought to India as well, so oncologists here can assess how the therapy works on Indian patients.

His other concern is affordability, as this drug, too, will be beyond the paying capacity of people in low- and middle-income countries (LMIC). (Reports suggest a treatment cost of over ₹75 lakh, for nine doses over six months.) It is often the case that a large section of people who need the drug are not able to afford it, he pointed out.

A World Health Organization report on access and inequity states that LMICs are disproportionately affected in terms of cancer cases and deaths, and, by 2040, these regions are expected to account for over 70 per cent of such deaths.

In its Global Oncology Trends report (2022), The IQVIA Institute notes that more novel cancer medicines became available for the first time this year and many of them employed immunology or precision biomarkers to transform the way patients are treated. “Adoption of breakthrough medicines and diagnostics is improving outcomes for millions around the world, though broad and equitable access remains a significant challenge to healthcare stakeholders — including patients,” it added.

Spotlight on immunotherapy

The dostarlimab trial also shines a light on immunotherapy, long identified by the pharmaceutical industry as a possible game-changer.

“It has changed the treatment landscape for many cancers,” says Dr Pramesh, citing lung and kidney cancers. In the dostarlimab trial, a subset of patients with colorectal cancer were chosen who were better disposed to the therapy.

Nevertheless, the findings have the scientific and patient community asking for more.

Dr T Raja, Director of Medical Oncology at Apollo Hospitals (Chennai) says, “We are already using immunotherapies for GI (gastro-intestinal) cancers, including rectal cancer, at our (cancer) centre with great results. We have several patients on immunotherapy in different types of cancers. Many are doing well. Hoping for long-term survival and possible cure in them.”

At Cancer Patients Aid Association, Executive Director Vinaya Chacko is hopeful, too. “There is much research being done, and it gives us a lot of hope that, in the years to come, more cancers will be successfully treated.” A hope that, this time around, the scientific community has indeed got “a foot in the door” towards finding a cure for cancer.