An experimental drug, administered to 12 patients battling rectal cancer under a clinical trial in the US, appears to have had "miraculous" and unprecedented impact on the patients, who experienced complete remission.

The drug called Dostarlimab was administered to the patients at Memorial Sloan Kettering Cancer Center in the US. The study based on the trial was published in The New England Journal of Medicine and lauded as revolutionary in the field of cancer research by the media.

The 12 patients were carefully monitored using magnetic resonance imaging, F-fluorodeoxyglucose–positron-emission tomography, and endoscopy. It was decided that patients who did not have a complete response were to receive subsequent standard radiation therapy and chemotherapy. However, all 12 patients witnessed complete disappearance of the tumour after six months of receiving the treatment.

Dr Luis A Diaz Jr, co-author of the study, said he did not know of any study that had eliminated cancer in the entire trial group in the past. "I believe this is the first time this has happened in the history of cancer," Dr Diaz said.

Even after a year, none of these patients needed traditional cancer treatment, and none had had cancer regrowth.

How Prevalent is Colorectal Cancer?

Colorectal cancer is a disease in which cells in the colon or rectum grow out of control, according to the Centers for Disease Control and Prevention. It is the third most diagnosed cancer and is the fourth leading cause of death worldwide, according to a 2019 study published in the World Cancer Research Journal. The study highlighted that, as per the demographic estimates, the global burden of colorectal cancer is expected to increase by 60% and could reach more than 2.2 million new cases and 1.1 million deaths by 2030.

Notably, more than two thirds of all cases and about 60% of all deaths occur in countries which have topped in the Human Development Index (HDI), including Hungary, Slovakia, Norway, The Netherlands, Denmark, among other European nations.

In 2020, there were over 1.6 million new cases of colorectal cancer – third-most common cancer in men and second-most common cancer in women, according to the World Cancer Research Fund International.

In India, the latest figures for colorectal cancer are not available, but as per the National Cancer Registry Program 2012-2014, the annual incidence rates (AARs) for colon cancer and rectal cancer in men were 5.36 and 5.17/100,000 people, respectively. The AAR for colon cancer in women was 4.3/100,000. This shows that men were comparably at higher risk than females. The report also highlighted that the risk of colorectal cancers was high amongst the Northeast population followed by southern India.

What is Dostarlimab and Why it's Not the Cure

Dostarlimab is a form of immunotherapy, said Dr Suparna Aji Rao, consultant oncologist with PD Hinduja Hospital in Mumbai. Similarly, Dr Sachin Wani, a consulting surgeon gastroenterologist, said the drug acts as a biological agent and acts against antibodies which can destroy the tumour.

"The drug helps stimulate the immune system to kill the tumour cells. This is given in an injectable form through saline. While it might look similar to a chemo drug it acts differently," explained Dr Rao.

Oncologists stressed on the fact that while this drug is promising, it is premature to call it a complete cure to colorectal cancer. "We cannot generalise it or extrapolate it to the rest of the populations across the world. But what is promising is that every patient that had enrolled in the trial saw complete eradication of the tumour cells," said Dr Rao.

Similarly, Dr Wani said, "The sample size is too small to jump to a conclusion and hence it is too early to call it a wonder drug."

According to both oncologists, there are several factors to take into consideration:

Firstly, the study was conducted on only 12 patients. Factors such as the total number and age of patients, the communities they come from, their ethnicities, their performance status need to be taken into consideration. "We will need data from across the world because we do not know how people from different ethnicities will react to this drug," said Dr Rao. "Again, this drug is not going to replace the current standard of care which is chemo radiation. This is something they have maintained in the study as well," she added.

Secondly, and most importantly, not all patients with rectal cancer are eligible for this drug. Those who will respond to this drug are those who carry the MMR deficient status. "Basically, they have certain characteristics which will make them sensitive to immunotherapy and that's hardly 5%-10% of all rectal cancer patients," said Dr Rao. This means that the results are applicable to only a small proportion of all patients with rectal cancer.

Thirdly, evaluation of treatment for one year is not enough. The oncologists spoke of how the study has seen results of up to only a year and doctors will have to wait for a few more years to actually decide if they need to replace all modalities of treatment with this drug. "A follow up for at least five years is required and multiple studies on hundreds of patients is necessary across the world to know whether this drug will replace the traditional standard of care," said Dr Wani.

Fourthly, since the drug costs over Rs 8 lakh, issues of accessibility would be one of the main concerns especially in developing countries. If the drug is seen to be useful in future studies, the cost needs to be reduced to make it affordable to patients of all communities.

There is a lot of excitement over immunotherapy because it is recent and promising. But the cost factor could be concerning for patients. It could be the major prohibitory factor when it comes to accessibility, Dr Rao concluded.