This was a small trial involving just twelve rectal cancer patients who were taking the same experimental drug. Nevertheless, the results are amazing. The cancer would indeed have disappeared in each of these people, becoming undetectable by physical examination, endoscopy, PET or MRI. Details of the study are published in the New England Journal of Medicine.
Colorectal cancers are the most common of all cancers, male and female combined. Those of the rectum represent 40% of these cancers and there are approximately 10,000 new cases per year in France. The majority of these diseases appear after the age of 60. As a reminder, the rectum is the terminal part of the digestive tract.
Surgery is the main treatment for rectal cancer from stage 2. Other remedies are also possible such as chemotherapy, radiotherapy or chemoradiotherapy. Survival of those affected is 63% five years after diagnosis. It is therefore necessary to find other approaches to combat the disease, which brings us back to this study.
The promise of dostarlimab
Researchers at the MSK Cancer Center in New York recently launched a small trial in hopes of helping patients avoid the potential side effects of surgery (proctectomy). This procedure, which aims to remove all or part of the rectum, can indeed cause permanent nerve damage and intestinal, urinary and sexual dysfunction.
The team became interested in dostarlimab. She suspected that the drug could help shrink or even eliminate tumors in patients based on previous trials with a drug in the same class called pembrolizumab. This had been proposed to patients with metastatic colorectal cancer (spread of tumors throughout the body) with a deficiency in the DNA mismatch repair system.
It should be remembered that this type of cancer (which tends to resist chemotherapy and radiotherapy) appears when the cellular DNA repair mechanisms are faulty. Normally, when cells make copies of their DNA, specific enzymes correct any “typo” that may occur in the genetic code. When the genes that code for these enzymes are faulty, cells end up accumulating faults, which can lead to cancer.
All in remission after two years
In this new trial, the researchers wanted to see what a similar drug could do for patients with cancer of this type, but which had not yet become metastatic. To do this, twelve people were recruited. All received five hundred milligrams of dostarlimab every three weeks for six months.
Initially, the researchers expected that most patients would still need to undergo the standard combination of chemotherapy, radiation therapy and possibly surgery after this treatment. Instead, the twelve patients’ cancers completely disappeared with dostarlimab alone. Their tumors were indeed undetectable on physical examination, endoscopy, PET and MRI.
To date, more than two years later, no patient has required chemoradiotherapy or surgery and the study authors note that no cases of progression or recurrence were noted during follow-up. “I believe this is the first time this has happened in the history of cancer, in that this is the first cancer trial in which every patient has gone into remission,” Dr. Luis Alberto Diaz, Jr., one of the trial leaders.
It is of course still too early to tell whether the patients will all remain in remission or whether the drug will work with different types of rectal cancer. As things currently stand, dostarlimab cannot yet replace standard curative treatments. However, these are really promising results.