In a small drug trial in the US, all of the patients treated for rectal cancer had their cancer go into remission. In what seems like a big step forward for treating rectal cancer, is this the big breakthrough in the long pursuit of a cure for cancer? While the outcome and results of this trial have only been positive, are there any side effects? How beneficial has this trial been, and will a new cancer treatment soon be available? Here’s what you need to know.
The experimental drug administered to the patients was an immunotherapy drug called dostarlimab, which is sold under the brand name Jemperli. It is used to treat endometrial cancer, but this was the first clinical test to see if it also worked on rectal cancer tumors. So far, the early results show that it seems to be surprisingly effective. The research team says that the fact that every trial patient’s cancer went away may be the first potential breakthrough for a cancer drug.
The lead author of a new paper about the results, medical oncologist Luis Diaz Jr. from Memorial Sloan Kettering Cancer Center (MSK), said, “I believe this is the first time this has happened in the history of cancer.”
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It’s important to note that the positive results have only been seen in 12 patients so far (the trial is still going on). All of these patients had tumors with a genetic mutation called mismatch repair deficiency (MMRd), which happens in about 5–10% of patients with rectal cancer.
Patients with these tumors tend to respond less well to chemotherapy and radiation treatments, which makes removing their tumors through surgery more critical.
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While MMRd mutations render current cancer treatments like chemotherapy and radiation ineffective, they make cancer cells more vulnerable to an immune response. If an immunotherapy agent boosts the immune response, such as a checkpoint inhibitor, it frees up immune cells so they can kill cancer cells more effectively.
Diaz explains: “When those mutations accumulate in the tumor, they stimulate the immune system, which attacks the mutation-ridden cancer cells. We thought, ‘Let’s try it before cancer metastasizes as the first line of treatment.”
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Usually, people with these kinds of rectal tumors would have to undergo chemotherapy and radiation therapy before the cancer could be removed surgically. Unfortunately, many of these treatments have long-term effects that can last the rest of the patient’s life.
Andrea Cercek, an MSK medical oncologist and the first author of the study, says, “The standard treatment for rectal cancer with surgery, radiation, and chemotherapy can be particularly hard on people because of the location of the tumor. They can suffer life-altering bowel and bladder dysfunction, incontinence, infertility, sexual dysfunction, and more.”
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So far, all of the procedures and side effects that come with them have been entirely avoided by the people who signed up for this trial. In the phase 2 study, patients got dostarlimab every three weeks for six months. They were even set to get standard chemoradiotherapy and surgery if the tumors ever came back. But no tumors or signs of tumors returned to date.
After six months of follow-up, all 12 patients in the trial showed a “clinical complete response,” which means that no tumors were detected using tests like MRI, PET, endoscopy, and biopsy. Sascha Roth, who was the first person to join the trial, stated, “Dr. Cercek told me a team of doctors examined my tests. And since they couldn’t find any signs of cancer, Dr. Cercek said there was no reason to make me endure radiation therapy.”
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It’s important to note that the research, which is being paid for by several groups, including the drug company GlaxoSmithKline, which makes Jemperli, isn’t over. So far, only preliminary results have been released. Currently, 12 people have finished the treatment and have been followed up for at least six months.
About three-quarters of patients have had mild or moderate side effects, such as rash, itching, tiredness, and nausea, but none of them has had their cancer return. The median follow-up is one year, but some patients, like Roth, have been cancer-free for two years.
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The trial is awaiting results from 30 people that have taken part in it. Only when more data is collected on the whole group will the researchers know more about how safe and effective dostarlimab is for people with rectal cancer. But a lot more research needs to be done on larger groups of patients.
Oncologist Hanna K. Sanoff of the University of North Carolina at Chapel Hill, who wrote a commentary on the findings, says, “Until such time, we need to treat the current results with both optimism and caution.”
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Sanoff thinks that clinical complete response to the treatment is not a good indicator of long-term cancer control. Even though checkpoint inhibitors like dostarlimab can have effects that last for years, cancer regrowth is still expected in a small number of patients whose tumors are treated without surgery, let alone with an experimental treatment like this one.
Sanoff explains, “Very little is known about the duration of time needed to find out whether a clinical complete response to dostarlimab equates to cure.” This explanation also points out that the results need to be repeated on a larger scale to be sure of the drug’s benefits, which have only been seen in a small number of patients with MMRd tumors so far. It is still unknown if the results of this small study done at Memorial Sloan Kettering Cancer Center can be applied to a larger group of people with rectal cancer.
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With all the positive results in mind, there is still a lot to be hopeful about. The researchers are already looking into whether their single immunotherapy approach could also help patients with other tumors that have MMRd, such as some types of stomach, prostate, and pancreatic cancer.
It’s early, and there’s still a lot left to learn about this treatment method, but Sanoff says that if more research can confirm the bright promise shown here, a new type of cancer treatment will soon be available.
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Despite these unknowns, Cercek, his colleagues, and the patients who gave up standard treatment in favor of immunotherapy’s promising but unknown future have provided extensive data on what may be an early look at a revolutionary shift in treatment, writes Sanoff. “If immunotherapy can be a curative treatment for rectal cancer, eligible patients may no longer have to accept functional compromise in order to be cured- Sanoff remarks.”
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