UH Seidman GI Oncologist Challenges the Colorectal Cancer Status Quo

Immunotherapy alone can achieve complete remission in select patients with colon and rectal cancer

Innovations in Cancer | February 2024

For the last two years, Sakti Chakrabarti, MD, a GI oncologist at UH Seidman Cancer Center, has been on a mission. He's been treating certain colorectal cancer patients, including those with early-stage diseases, with immunotherapy with great success. At the same time, he's been collecting information from other cancer centers nationwide and putting it into a large database called 'DREAM-GI.' This is all to make progress in the field of cancer treatment.

Sakti Chakrabarti, MD

The goal, he says, is nothing short of radically altering the standard of care for colorectal cancer patients who generally need surgery and often chemotherapy.

“A lot of people don't realize that some colon cancers can be put in complete remission and potentially be cured without surgery or radiation or chemotherapy,” Dr. Chakrabarti says.

A less invasive approach like treatment with immunotherapy is especially needed for older adults with colorectal cancer who are at risk of complications from surgery and chemotherapy, he says. Approximately one in five colon cancer patients who ordinarily require surgery harbor a specific genomic signature known as microsatellite instability-high (MSI-H), which makes them exquisitely sensitive to immunotherapy.

“I have seen quite a few older patients with stage 2 and 3 colon cancer, where the standard of care is surgery, and the surgeon was hesitant to do surgery because of their other health problems,” he says. “When surgery can be detrimental for a given patient, immunotherapy is a better option for this MSI-H subset of patients.”

Among the various immunotherapy agents, pembrolizumab is a common one. A typical course of pembrolizumab is a 30- to 45-minute infusion every three weeks for six months to a year. Most patients tolerate the treatment well without significant side effects, if any. In fact, Dr. Chakrabarti and UH Seidman colleagues conducted a systematic review of clinical trials that utilized pembrolizumab alone, concluding that severe immune-related adverse events in GI cancer patients receiving pembrolizumab monotherapy are uncommon.

“This underscores the safety profile of this therapy in patients with GI cancer,” he says.

At UH Seidman, Dr. Chakrabarti is primarily using pembrolizumab to treat colorectal cancer patients with stage 1, 2, or 3 disease whose tumor displays the microsatellite instability-high (MSI-H) signature.

“Since these patients account for roughly 15 to 20 percent of patients with colon cancer, it’s not a trivial number,” he says.

“If patients have this signature in their tumor, pembrolizumab can work very well for them,” Dr. Chakrabarti says. “This is the part which is underexploited. This information is not widely known or discussed.”

Dr. Chakrabarti is determined to change that. He recently presented his data from the DREAM-GI database at a meeting of the American Society of Clinical Oncology in San Francisco. It showed a response rate of 75% among unselected GI cancer patients. The response rate is higher in colon and rectal cancer patients.  

“Immunotherapy is associated with remarkable response rate and durability in patients with dMMR/MSI-H GI cancers,” he says. “Progression of cancer on immunotherapy is rare. These real-world data support further investigation of non-operative approaches for patients with MSI-H gastrointestinal cancers.”

Improving Outcomes in Black Patients with GI Cancers

On another front, Dr. Chakrabarti is also seeking to change the status quo. He’s received a large grant from an industry sponsor to improve health equity among Black patients treated for GI cancer at UH Seidman.

Biomarker testing in GI cancer patients can open up treatment opportunities. The upcoming project, EQUITY-GI, wants to ensure a biomarker testing rate of at least 80% in Black GI cancer patients.

“We all know that information is power, and it is important to use the right information at the right time,” he says.

The project includes technology to ensure biomarker testing, counseling to increase enrollment in clinical trials, and healthy literacy interventions to help patients better understand the nuances of their cancer treatment.

“We will closely work with the treating physician to make sure biomarker testing, including the genomic profiling, is done for each patient, with the appropriate treatment executed according to the biomarker profile,” he says. “That will give our patients the best chance of survival.”

For more information, visit Immunotherapy for Colorectal Cancer or email Sakti Chakrabarti, MD at Sakti.Chakrabarti@UHhospitals.org.