Cancer clinical trials include treatment, prevention, screening, supportive and palliative care and natural history studies. Clinical trial success rates vary greatly, but oncology drugs are the least likely to succeed, with only a 3.4% success rate. But a recent clinical trial at Memorial Sloan Kettering Cancer Center (MSK) blew that statistic out of the water when 100% of participants showed no evidence of cancer after treatment.
Small But Impressive Study
Eighteen adults diagnosed with rectal cancer — and stage 2 or 3 rectal tumors — faced chemotherapy, radiation and life-altering surgery with risks of severe side effects such as urinary, sexual and bowel dysfunction that could result in a need for colostomy bags.
However, after participating in a trial in which they were put on an immunotherapy drug for six months, each patient was found to be free of tumors and in complete remission from their cancers.
MSK shared a video with four patients who participated in the clinical trial explaining how it changed their lives.
— Memorial Sloan Kettering Cancer Center (@MSKCancerCenter) June 5, 2022
Building Upon Previous Work
Dr. Luis A. Diaz Jr., who led the study alongside medical oncologist Andrea Cercek, conducted a previous trial for a Merck checkpoint inhibitor; the results were released in 2017. This type of immunotherapy blocks immune checkpoint proteins on the surface of immune cells (T-cells) from binding with partner proteins. When this binding happens, it sends a signal to the immune cell that prevents it from destroying cancer cells.
That previous study treated 86 patients with metastatic cancer. Of those, 66 patients experienced their tumors shrinking substantially and stabilizing. The results caused Dr. Cercek and Dr. Diaz to wonder what would happen if immunotherapy was used before the cancer spread. They hoped that immunotherapy, which harnesses the body’s immune system, would shrink the tumors as much as possible, improving the success and decreasing the harsh effects of other treatments.
Using Immunotherapy To Treat Cancer
All of the participants in the new trial had tumors with a specific genetic makeup known as mismatch repair-deficient (MMRd) or microsatellite instability (MSI), which have a unique response to immunotherapy. Introducing a checkpoint inhibitor allows the body’s immune cells to recognize cancer cells as ones that aren’t normal and must be attacked.
“When the brakes are taken off the immune cells, MMRd cells look especially strange because they have so many mutations. So the immune cells attack with much more force,” Dr. Cercek explained to Memorial Sloan Kettering Cancer Center News.
The patients were given checkpoint inhibitor dostarlimab (also known by its GlaxoSmithKline brand name, Jemperli) intravenously every three weeks for six months. Doctors closely tracked the tumors using endoscopy and other methods. Not only did the tumors shrink, but in every case, the cancer disappeared following immunotherapy.
Researchers Are Optimistic, But More Research Is Needed
“The most exciting part of this is that every single one of our patients has only needed immunotherapy,” Dr. Cercek told MSK News. “We haven’t radiated anybody, and we haven’t put anybody through surgery. They have preserved normal bowel function, bladder function, sexual function, fertility. Women have their uterus and ovaries. It’s remarkable.”
In addition, all of the trial participants have remained cancer-free for up to two years.
Dostarlimab is approved by the U.S. Food and Drug Administration to treat endometrial cancer with dMMR. Treatment of rectal cancer is an off-label use.
“Now, we’re faced with a new set of questions,” Diaz told MSK News. “Could the therapy work on people who are high-risk before the cancer even develops? What about even pre-diagnosis? To me, this is very exciting because it alters the course of how we treat cancer and redefines anti-cancer therapeutics.”