A clinical trial involving dostarlimab, an anti-PD-1 monoclonal antibody, has reportedly led to 100% complete responses in a group of 18 patients with advanced-stage mismatch repair-deficient (dMMR) rectal cancer, according to researchers at the Memorial Sloan Kettering Cancer Center (MSKCC) in New York City.
According to reports, at the end of the 6-month study, no evidence of tumor came up during follow-up MRIs of 14 patients, with the follow-up ranging from 6 to 25 months where no patient received additional therapy.
Meanwhile, the rest of the four patients, who had limited follow-up, demonstrated preliminary evidence of response, with one showing a clinical complete response.
Andrea Cercek, MD, MSKCC, stated that during the course of the clinical study, the PD-1 blockade was well tolerated, and none of the patients developed grade 3 or 4 adverse events.
The results of the study were reported at the annual meeting of the American Society of Clinical Oncology (ASCO) in New York City. The outcomes were also published in the New England Journal of Medicine.
Cercek stated that none of the patients needed surgery, radiation, or chemotherapy, and there was no disease recurrence noted in the follow-up period.
She further stated that the data provides the basis for immunoablative therapies and signifies the clinical impact of biomarker-driven therapy in treating early-stage disease.
Cercek added that those with early-stage of tumor-agnostic mismatch repair deficiency can avoid surgery, chemotherapy, and radiation, which will be beneficial for those who do not have access to modern radiation, chemotherapy, and surgery.
Cercek added that a longer follow-up period is required to establish the treatment’s durability.
However, Kimmie Ng, MD, MPH, at Dana-Farber Cancer Institute, Boston, stated that while the results are scientifically plausible and clinically meaningful, they cannot be considered practice-changing right now.
Ng noted several reasons for that, such as the sample size and the median follow-up being comparatively small, and participants being enrolled at just one institution, which is also reputed for non-operative treatment of rectal cancer.
Moreover, there is no data on survival or other clinically relevant endpoints, only the overall response.
Ideally, such issues are addressed in a randomized clinical trial, but with the condition being rare, Ng said it would not be possible.
Source credit: https://www.medpagetoday.com/meetingcoverage/asco/99071