• Rectal cancer can be serious, impacting thousands of people in the United States annually.
• Treatment options for rectal cancer vary based on the type and severity.
• A recent study found that treatment with immune checkpoint inhibitors can yield highly positive results among people with a specific subtype of rectal cancer.

While cancer continues to claim many lives, research on treatment options is constantly improving and expanding. One area of recent development is in the treatment of rectal cancer.

A recent study published in The New England Journal of Medicine found that treatment involving immune checkpoint inhibitors may be extremely effective among people with a specific type of rectal cancer.

It may be effective enough that other forms of follow-up treatment like surgery are unneeded in people with this type of cancer.

Rectal cancer treatment options

Cancers of the colon and rectum, collectively called colorectal cancer, impact thousands of individuals each year. The National Cancer Institute estimates that, in 2022, there will be 151,030 new cases of colorectal cancer and 52,580 deaths from colorectal cancer in the U.S.

The sobering statistics indicate that “[c]olorectal cancer is the second leading cause of cancer death in the United States.”

When it comes to the treatment of rectal cancer, the American Cancer Society notes that the approach mainly depends on the stage of the tumor. Surgical removal is the primary approach when rectal cancer has not spread to other areas, with possible additional radiation and chemotherapy.

Chief Scientific Officer of the American Cancer Society, Dr. William Dahut, explained it this way to MNT:

“Rectal cancer, traditionally, has been treated with a combination of chemotherapy, radiotherapy, and surgery. So, it’s [a] very intensive treatment. The chemotherapy is toxic — not easy to take — and the side effects of radiation and surgery are not trivial. […] There are patients who can be [successfully treated]. […] It is not an easy road, and oftentimes, there are long-term side effects from the therapy alone.”

But researchers are looking into other treatment options based on particular subtypes of rectal cancer.

Immune checkpoint inhibitors

The study involved participants with a highly specific type of rectal cancer classified as locally advanced, mismatch repair-deficient rectal cancer. The study authors theorized that this type of cancer could be effectively treated using a type of immunotherapy. Immunotherapies help the body identify and better fight cancer cells.

Researchers specifically utilized an immune checkpoint inhibitor called a PD-1 inhibitor. The use of a PD-1 inhibitor aims to prevent cancer cells from evading the immune system. The study included 12 adult participants with either stage 2 or stage 3 mismatch repair-deficient rectal cancer. Participants received the PD-1 inhibitor, dostarlimab intravenously every 3 weeks for over 6 months.

The participants responded well to this treatment. All of them had no evidence of tumors by the end of the trial, and none of them have had to undergo additional surgery or chemoradiotherapy since. Currently, all the participants have completed at least 6 months of follow-up.

Prof. John Bridgewater, a clinical researcher from the University College London Cancer Institute specializing in gastrointestinal medical oncology, who was not involved in this trial, was enthusiastic about its results. He told MNT:

“These data report the highly effective use of immunotherapy, specifically, an inhibitor of the checkpoint called the programmed death receptor 1 (PD1) in patients with mismatch repair-deficient rectal cancer […] This is a significant advance in that it obviates the need for surgery or radiation therapy for these cancers, both conventional treatments with many complications and side effects.”

Limitations and areas for further study

While the study offers some good news, it is not without limitations. For example, researchers used several methods to confirm the absence of cancer.

Still, since none of the participants have undergone surgery, the researchers have not used this method to evaluate the cancer’s absence. They also note that further research can seek to determine why the use of checkpoint inhibitors is not as effective in metastatic colorectal tumors.

The significant drawbacks of the study were its small size and limited follow-up time. Currently, not all the participants have had a 12-month follow-up.

The study authors caution that “[t]hese findings must be reproduced in a larger prospective cohort that balances academic and community practices and ensures the participation of patients from a diverse set of racial and ethnic backgrounds.”

Dr. Dahut noted that this study adds to growing evidence that understanding the type of cancer present impacts treatment. He explained to MNT:

“Patients should really be empowered to understand the biology of their cancer. […] [W]ork was done that let patients know that they had a particular subtype of rectal cancer. It really shows the power of biomarkers and precision medicine. If you treated all patients with rectal cancer with a checkpoint inhibitor, you wouldn’t see this response rate. So wherever patients are, it’s important that they’re talking to their doctors and learning as much about their cancer as they can. Their therapies may be vastly different based on those results.”

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