Imfinzi Combo Cuts Risk of Death by 25% in Advanced Biliary Tract Cancer

Patients with advanced biliary tract cancer lived longer on Imfinzi (durvalumab) plus chemotherapy than on chemotherapy alone, according to four-year follow-up data from the phase 3 TOPAZ-1 trial.

Patients with advanced biliary tract cancer had a 25% lower risk of dying at any point during the study when treated with Imfinzi plus chemotherapy compared with chemotherapy alone, according to the post hoc analysis (meaning the researchers went back and took a fresh look at the trial's data well after the main results were first reported).

"Based on the results of TOPAZ-1, [Imfinzi] plus [gemcitabine and cisplatin] has been established as a first-line treatment and standard of care for patients with [advanced biliary tract cancers]," the researchers wrote.

Researchers followed patients for close to four years after the last person joined the study, making this the longest follow-up so far for an immunotherapy and chemotherapy combination used as a first treatment for this cancer.

What did the TOPAZ-1 post hoc study find?

The trial included 685 patients whose biliary tract cancer could not be removed with surgery or had spread locally or to other parts of the body. Almost half of patients received Imfinzi plus the chemotherapy drugs gemcitabine and cisplatin, a combination researchers call GemCis. The other half received a placebo plus the same two chemotherapy drugs.

By the four-year mark, patients who received Imfinzi lived a median of 13 months, compared with 11.4 months for those who received chemotherapy alone.

The survival gap between the two groups widened the longer researchers followed patients. At two years, 23.2% of patients on Imfinzi were still alive, compared with 13.7% on placebo. At three years, it was 15% versus 7.6%, respectively. By four years, 11.8% of patients on Imfinzi were alive, compared with 4.3% on placebo — more than twice as many.

After the trial's main treatment ended, many patients in both groups went on to receive further cancer treatment, most often more chemotherapy. Among patients in the placebo group, 8.1% later received immunotherapy, compared with 3.8% of patients who had already received Imfinzi. A small number of patients — four who had received Imfinzi and one who had received placebo — were treated again with Imfinzi plus chemotherapy after their cancer returned.

How was the TOPAZ-1 trial designed?

TOPAZ-1 enrolled patients between April 2019 and December 2020 at 105 hospitals in 17 countries. Patients were randomly split into two equal groups. One group received Imfinzi through an IV at a dose of 1,500 milligrams, plus gemcitabine and cisplatin. The other group received a placebo plus the same two chemotherapy drugs. Everyone received treatment on day one and day eight of a three-week cycle, for up to eight cycles. After that, patients continued receiving Imfinzi or placebo monotherapy every four weeks until their cancer worsened or side effects became too difficult to continue.

Imfinzi already met the trial's primary end point of overall survival when TOPAZ-1's initial results were reported; this analysis reflects a longer follow-up of the same patients.

What side effects did patients experience?

The most common serious side effects among patients who received Imfinzi were cholangitis, an infection or inflammation of the bile ducts (7.4%); fever (4.4%); low red blood cell counts, known as anemia (3.6%); and sepsis, a serious blood infection (3.6%). Among patients who received placebo plus chemotherapy, the most common serious side effects were cholangitis (5%) of patients, sepsis (2.6%), fever (2.3%) and abdominal pain (2.3%).

Side effects serious enough to cause patients to stop treatment occurred in 6.2% of the Imfinzi group and 5.3% of the placebo group. Side effects related to the immune system, which can happen because Imfinzi works by boosting the immune system, were more common in the Imfinzi group (30.2%) than the placebo group (20.8%).

By the four-year mark, 90.3% of patients who received Imfinzi and 94.8% of patients who received placebo had died. In both groups, the cancer itself was by far the most common cause of death, rather than treatment side effects. Death from a side effect alone was rare, happening in just 1.2% of patients in each group.

References

1. "Durvalumab Plus Chemotherapy for Advanced Biliary Tract Cancer: A Post Hoc Analysis of the TOPAZ-1 Randomized Clinical Trial." JAMA Oncology. Oh D-Y, et al. Published July 9, 2026.