Rectal Cancer Study Produced Very Promising Treatment Results

The cure rate for nonmetastatic rectal cancer has been improving for decades but often includes unpleasant treatments, wrote Hanna K. Sanoff, M.D., M.P.H. in an Editorial published by The New England Journal of Medicine (NEJM) on June 5, 2022.

Recent phase 3 trial findings have increased treatment intensity to include multiagent chemotherapy in addition to radiation therapy before proctectomy is performed.

Such treatment has resulted in a 3-year disease-free survival rate of up to 77%.

Unfortunately, this treatment approach is grueling and can cause significant long-term sequelae, including neuropathy, infertility, and bowel and sexual dysfunction. 

However, a recent, limited phase 2 clinical study’s results offer a promising treatment alternative.

In this study, colorectal cancer vanished in the participating patients.

This study found mismatch repair–deficient, locally advanced rectal cancer was highly sensitive to single-agent PD-1 blockade.

A total of twelve patients completed treatment with dostarlimab and underwent at least six months of follow-up. 

All patients (100%; 95% confidence interval, 74 to 100) had a complete clinical response, with no evidence of tumor on magnetic resonance imaging, 18F fluorodeoxyglucose positron-emission tomography, endoscopic evaluation, digital rectal examination, or biopsy. 

At the time of this report, no patients had received chemoradiotherapy or undergone surgery, and no cases of progression or recurrence had been reported during follow-up (range, 6 to 25 months). 

And no adverse events of grade 3 or higher have been reported.

Dr. Luis A. Diaz Jr. of Memorial Sloan Kettering Cancer Center, the paper’s author, published in the NEJM describing the results, said he knew of no other study in which a treatment completely obliterated a cancer in every patient.

“I believe this is the first time this has happened in the history of cancer,” Dr. Diaz said, reported The New York Times on June 7, 2022.  

The authors commented that although the results of this study are promising, it is a small study and represents the experience of a single institution. These findings must be reproduced in a larger prospective cohort that balances academic and community practices and ensures the participation of patients from diverse racial and ethnic backgrounds.

“Very little is known about the duration of time needed to determine whether a complete clinical response to dostarlimab equates to cure,” Dr. Sanoff wrote in the NEJM editorial.

Dostarlimab, sold under the brand name Jemperli, is a monoclonal antibody used as a medication for the treatment of endometrial cancer.

On August 17, 2021, the U.S. FDA granted accelerated approval to GlaxoSmithKline LLC using dostarlimab-gxly for adult patients with mismatch repair-deficient recurrent or advanced solid tumors, as determined by an FDA-approved test that has progressed on or following prior treatment and who have no satisfactory alternative treatment options.

The study was supported by the Simon and Eve Colin Foundation, GlaxoSmithKline, Stand Up to Cancer, Swim Across America, and the National Cancer Institute of the National Institutes of Health. No industry conflicts of interest were disclosed.

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