Antibiotic use doesn’t appear to disrupt the effectiveness of the immune checkpoint inhibitor durvalumab in advanced biliary tract cancer, according to a new analysis of the landmark TOPAZ-1 clinical trial.
The findings, released at the ASCO Gastrointestinal Cancers Symposium 2023, suggest that “people with advanced biliary tract cancer can safely be treated with antibiotics while still benefiting from treatment with durvalumab plus chemotherapy,” said lead author Aiwu Ruth He, MD, PhD, a gastrointestinal oncologist with MedStar Georgetown University Hospital, Washington.
Antibiotic use during immune checkpoint inhibitor therapy has been associated with poorer outcomes. A review of 12 studies published in Frontiers in Oncology found that antibiotic use was associated with worse progression-free and overall survival.
“Patients with biliary tract cancer have the increased risk of biliary tract infection as the result of biliary tract obstruction, and they often receive antibiotics,” Dr. He said.
A 2020 report in eCancer suggested that antibiotics may disrupt gut bacteria and, as a result, interfere with the immune system’s responsiveness. “It has been a consensus that the use of broad-spectrum antibiotics should be avoided during the use of immunotherapy whenever possible,” the report authors wrote. “In addition, antibiotics should be prescribed only when properly indicated.”
However, cutting down on antibiotic use may be especially difficult in cancer patients since they frequently suffer from infections. “An antibiotic-resistant bacterial infection may cause serious issues for a cancer patient, who likely already has a suppressed immune system,” according to a 2017 information sheet posted by the Cancer Treatment Centers of America. “Chemotherapy may cause neutropenia, a reduction of white blood cells that help fight infections and viruses. Radiation therapy may damage the skin and cause irritation and wounds. Immunotherapy or targeted therapy drugs may trigger side effects that may lead to infections. Incisions from surgery or to insert ports or catheters may be vulnerable to infections.”
The new study
For the new subgroup analysis, researchers analyzed data from the phase 3 TOPAZ-1 clinical trial, which was a double-blinded analysis of durvalumab plus gemcitabine and cisplatin in advanced biliary tract cancer. The previously reported main findings from the study were positive with a median overall survival of 12.8 months in the durvalumab arm versus 11.5 months in the placebo arm (hazard ratio, 0.80; P = .021). These findings contributed to the Food and Drug Administration’s decision in 2022 to approve the treatment for use in locally advanced or metastatic biliary tract cancer.
Of 341 patients who received durvalumab treatment, 167 also took antibiotics. The median overall survival in the antibiotic and nonantibiotic groups were similar at 12.6 months (95% confidence interval, 9.7-14.8 months) and 13 months (95% CI, 10.8-14.7 months), respectively. Median progression-free survival was 7.3 months (95% CI, 6.5-7.7 months) and 7.2 months (95% CI, 5.9-7.4 months), respectively.
“The results support that advanced patients’ risk of death, and the risk that their cancer would grow, spread, or get worse, was not meaningfully different between patients who used antibiotics and those who did not use antibiotics at the same time as they were receiving durvalumab-based treatment,” Dr. He said. “The result is not surprising to me since it is not clear to me how and why antibiotics may affect the effectiveness of immunotherapy.”
Moving forward, she said, “additional studies are needed to further investigator the relationship between antibiotics use and effectiveness of immunotherapy. We need to understand why use of antibiotics during treatment with immunotherapy is correlated with poor outcomes in some circumstances but not in other circumstances.”
The study was funded by AstraZeneca. The Gastrointestinal Cancers Symposium is sponsored by the American Gastroenterological Association, the American Society for Clinical Oncology, the American Society for Radiation Oncology, and the Society of Surgical Oncology.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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