Adding Roche's immunotherapy drug Tecentriq to standard chemotherapy after surgery led to a 50% reduction in cancer recurrence and death among colon cancer patients with a specific genetic defect, according to trial data presented at the American Society of Clinical Oncology meeting in Chicago.
The breakthrough specifically benefits patients whose tumors have deficient DNA mismatch repair (dMMR), a genetic defect found in about 15% of colon cancer cases. These dMMR tumors typically do not respond well to chemotherapy alone, representing a significant unmet medical need.
Trial Design and Results
The phase 3 trial enrolled 712 patients with dMMR stage 3 colon cancer that had been surgically removed and showed cancer cells in their lymph nodes. Half of the study participants received chemotherapy combined with Tecentriq for six months, followed by Tecentriq alone for another six months. The control group received chemotherapy for 12 months.
Tecentriq, which activates the immune system to attack and kill cancer cells, demonstrated benefits even in the oldest patients and those at particularly high risk for recurrence.
"The findings from our study represent a major advance in the adjuvant treatment of dMMR stage 3 colon cancer and will now change the treatment for this type of cancer," said study leader Dr. Frank Sinicrope of the Mayo Clinic in Rochester, Minnesota.
Clinical Significance
The results address a critical gap in treating colon cancer patients whose tumors carry the dMMR genetic defect. Traditional chemotherapy has shown limited effectiveness in this patient population, making the 50% reduction in recurrence and death particularly significant.
"It's extremely rewarding to be able to offer our patients a new treatment regimen that can reduce the risk of recurrence and improve their chances of survival," Sinicrope noted.
The study's findings suggest that immunotherapy may be particularly effective in dMMR colon cancer due to the genetic characteristics that make these tumors more recognizable to the immune system. This represents a shift toward precision medicine approaches that target specific molecular subtypes of cancer.
Treatment Protocol
The successful treatment protocol involved a two-phase approach: an initial six-month period combining chemotherapy with Tecentriq, followed by six months of Tecentriq monotherapy. This 12-month total treatment duration showed superior outcomes compared to the standard 12-month chemotherapy regimen.
The trial's success in high-risk and elderly patients suggests the treatment approach could benefit a broad range of patients within the dMMR colon cancer population, potentially establishing a new standard of care for this specific molecular subtype.
