Remarkable Drug Trial Ends With All 18 Patients Cancer-Free

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A cancer treatment has shown amazing results in a small clinical trial. All of the treated patients, who had a specific form of mid-stage rectal cancer, have since experienced complete remission. Although the findings are based on a sample size of just 18 people, they could hold important implications for treating these particular cancers.

The results of the Phase II trial were published over the weekend in the New England Journal of Medicine. The study involved researchers at the Memorial Sloan Kettering Cancer Center as well as Yale University, and it was sponsored by the pharmaceutical company GlaxoSmithKline.

The trial enrolled volunteers diagnosed with stage II or III rectal cancer, meaning their tumors had begun to grow larger and spread to nearby parts of the body. Their cancer was also determined to be caused by a particular mechanism known as a deficiency in mismatch repair.

Cancers can form for many different reasons. But sometimes, our cells develop mutations that hinder them from being able to fix errors made when DNA is copied within them. These errors can then eventually lead to cancerous cells.

The researchers theorized that their treatment, a lab-made antibody called dostarlimab, might be able to help this subset of patients. It works by inhibiting a protein known as programmed death receptor-1 (PD-1) found in many cancer cells. This inhibition then allows the immune system to recognize the cancer cells as harmful and target them for destruction. The drug was developed by GlaxoSmithKline, and it was given an accelerated approval by the Food and Drug Administration last year for cases of endometrial cancer linked to a mismatch repair deficiency.

The patients were given a dose of dostarlimab every three weeks for six months. After that, per the original plan, they would be given standard chemoradiotherapy and surgery if their tumors still could be detected. But remarkably, the treatment alone seemed to wholly eradicate their cancer. As of the study’s publication, 18 patients have completed treatment, while 12 have been tracked for at least a year, and none of them have shown signs of their cancer returning so far.

Cancers are notoriously resistant to treatment, and few if any drugs on their own ever have shown the sort of success seen here. “I believe this is the first time this has happened in the history of cancer,” study author Luis A. Diaz Jr. of Memorial Sloan Kettering Cancer Center told the New York Times. According to the New York Times, the first patient given the drug has remained cancer-free two years later.

That said, the findings are still very early, and it will take much more research with larger-sized studies to confirm the drug’s effectiveness, especially over the long term. Dostarlimab and similar immunotherapy treatments also aren’t side-effect free, and they can rarely cause serious complications like muscle weakness, though no such adverse events were reported in this trial. And the drug doesn’t come cheap, costing $11,000 per dose out of pocket.

But if these findings are further validated, they could very well lead to a new standard of care for these kinds of cancers. Mismatch repair deficiency is most commonly linked to colorectal cancer, but it can also help cause cancers of the breast, thyroid, bladder, and prostate, among others. And the results here suggest that PD-1 inhibitors might help people with these tumors avoid more grueling treatments, if used early enough in the cancer’s development, before it spreads throughout the body.

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