A small phase 2 trial of a new drug for rectal cancer caused remission in 100% of the trial participants.
Results from a recently finished drug trial offer hope for the treatment of rectal cancer. According to the team at Memorial Sloan Kettering Cancer Center, all 12 trial participants had early-stage rectal cancer. After just six months of the experimental therapy, 100% of the patients saw a complete disappearance of their tumors. This is the first time that an experimental treatment has managed to achieve such groundbreaking results.
I don’t think anyone has seen this before, where every single patient has had the tumor disappear.
Dr. Andrea Cercek, study author
The team of researchers recruited 12 adults with stage II or stage III rectal cancer. None of the participants had received any form of chemotherapy, radiation, or immunotherapy prior to the trial. Moreover, all trial participants had mismatch repair-deficient rectal cancer.
Approximately 5-10% of all rectal adenocarcinomas are mismatch repair-deficient and respond poorly to the currently available standard treatments. Therefore, researchers aimed to assess the effectiveness of a new cancer drug in patients with the disease. As part of the trial, the participants received the drug every three weeks for a total of six months. Following the treatment, they underwent standard chemoradiotherapy and surgical resection. However, those who achieved complete remission following treatment did not receive chemoradiotherapy and surgery.
After a 12-month follow-up, researchers noted a complete disappearance of cancer. A multitude of tests was conducted prior to and after the treatment. These included MRI scans, PET scans, digital rectal examination, endoscopic examination, and biopsy. However, the tumor did not show up on any of the tests post-treatment.
I believe this is the first time this has happened in the history of cancer.
Dr. Luis A. Diaz Jr., study author
The complete trial results are available in the New England Journal of Medicine.
Third Most Common Cancer
Approximately 98% of rectal cancers are adenocarcinomas. Most cases present with rectal bleeding, altered bowel habits, and abdominal pain. However, patients may also complain of urinary symptoms from the tumor pressing on the bladder or prostate. Recent advancements in medicine and surgery have significantly increased the survival rates for patients.
Locally advanced rectal cancer is typically treated using neoadjuvant chemotherapy and radiation followed by surgical resection. However, these treatments can often lead to complications such as scarring of the uterus, bowel and bladder dysfunction, and sexual dysfunction. Patients that undergo resection of the rectum end with a permanent colostomy bag. Thus, further complicating matters.
Surgery and radiation have permanent effects on fertility, sexual health, bowel, and bladder function. The implications for quality of life are substantial, especially in those where standard treatment would impact childbearing potential. As the incidence of rectal cancer is rising in young adults, this approach can have a major impact.
Dr. Andrea Cercek, study author
Moreover, 5 to 10% of rectal adenocarcinomas are mismatch repair-deficient. Due to gene mutations, these tumor cells are unable to correct any DNA mistakes. As a result, the immune system is unable to recognize and kill these cells. Moreover, these types of rectal cancers respond poorly to standard chemotherapy drugs.
Previously researchers have successfully used immune checkpoint blockade as a first-line treatment for patients with metastatic mismatch repair-deficient colorectal cancer. And for patients with the treatment-refractory disease. The treatment achieved an objective response rate of 33-55% and increased survival rates for the patients. Therefore, based on these findings, the team planned to test the effectiveness of single-agent programmed death 1 (PD-1) blockade for locally advanced mismatch repair-deficient rectal cancer.
How Does the Cancer Drug Work?
The PD-1 inhibitor, dostarlimab was developed by GlaxoSmithKline.According to Dr. Andrea Cecek at Memorial Sloan Kettering Cancer Center in New York, dostarlimab boosts the immune system, helping it recognize and attack cancer. The phase 2 trial aimed to assess the effectiveness of first-line treatment with dostarlimab for locally advanced mismatch repair-deficient rectal cancer.
They lack a gene that enables them to repair their DNA and because of that, they have many, many mutations, and the immune system recognizes the cancer is foreign. When we give immunotherapy, like dostarlimab, it really just revs up the immune system so that it sees the cancer and gets rid of it.
Dr. Andrea Cecek, study author
Out of the 16 study participants. 12 had completed their treatment and had undergone at least 6 months of follow-up. According to the study, all 12 participants had a clinical complete response, as evident on MRI scans, digital rectal examination, and visual endoscopic inspection. Furthermore, PET scans and biopsies demonstrated the absence of tumor.
None of the 12 patients experienced any severe adverse events. The most common side effects included a rash or fatigue. According to researchers, none of the participants needed chemotherapy, radiotherapy, or surgery after the treatment. Moreover, no recurrence or progression occurred.
Although the results are promising, researchers caution that the trial is too small to infer conclusions. A longer follow-up can assess the drug’s duration of response and whether the trial participants require any surgical resection in the future.
The trial is currently ongoing. Four other patients are still receiving treatment and have so far shown similar promising results.
Reference:
Andrea Cercek et al, PD-1 Blockade in Mismatch Repair–Deficient, Locally Advanced Rectal Cancer, New England Journal of Medicine (2022). DOI: 10.1056/NEJMoa2201445
