A group of rectal cancer patients saw their tumors disappear after they received an experimental drug called dostarlimab, and none of the patients experienced significant side effects from the treatment.
"I believe this is the first time this has happened in the history of cancer, in that every patient entered remission in the trial," said Dr. LuisAlbertoDiaz, Jr., one of the trial leaders.
It's too early to say if the drug will work for everyone with rectal cancer, but the results are cause for optimism. The details of the trial were published in the New England Journal of Medicine.
The 12 trial participants all have a type of rectal cancer that is resistant to treatment and is known as "mismatched repair- deficient" rectal cancer. This type of cancer arises when cells' repair mechanisms fail. Normally, as cells make copies of their genetic code, specific enzymes work to correct any mistakes. According to the National Cancer Institute, when the genes that code for these copy-editing enzymes are faulty, cells end up accumulatingDNA that can lead to cancer.
Patients were not responding to therapy. They received a transplant.
According to the report, 5% to 10% of rectal cancer patients are mismatch repair deficient. A proctectomy is a surgery to remove all or part of the rectum, which can cause permanent nerve damage, as a result of the cancer's resistance to treatment.
Potential side effects of surgery are something the researchers are trying to help patients avoid.
They suspected that dostarlimab might help shrink or eliminate patients' tumors based on previous trials with a drug of the same class. Pembrolizumab and dostarlimab boost the immune cells' ability to attack cancer cells.
Patients with tumors that had begun to spread were the first to benefit from pembrolizumab. The drug helped patients to shrink their tumors and prolong their lives. In the new trial, the researchers wanted to find out if a similar drug could be used to treat patients with local cancer that has not yet spread.
Dostarlimab was given to the trial participants for six months. The initial expectation was that most of the patients would have to go through the standard combination of therapy. All of the patients' cancers were cleared on dostarlimab alone. Their tumors were not visible when they were examined. The team wrote in their report that none of the patients needed further treatment after a year.
More than two years later, no patients have required surgery, and no cases of progression or recurrence have been noted during follow-up.
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"These results are cause for great optimism, but without further research, dostarlimab cannot yet replace the standard, curative treatment for mismatch repair- deficient rectal cancer," Dr. Sanoff wrote.
She wrote that in some cases, patients' responses can last for a long time, but in others, the effects wear off quickly. About 20% to 30% of patients have their condition managed without surgery. Sanoff said that little is known about how long it will take to find out if a clinical complete response to dostarlimab equates to cure.
There could be a dramatic shift in how rectal cancer is treated in the future according to the new trial results. She said that if immunotherapy can be a cure for rectal cancer, eligible patients may no longer have to compromise.
"While longer follow-up is needed to assess response duration, this is practice-changing for patients with mismatch repair- deficient rectal cancer."
It was originally published on Live Science
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