TOPAZ-1 is the phase 3 clinical trial that made immunotherapy part of the standard first-line treatment for advanced biliary tract cancer, a group of aggressive tumors arising in the bile ducts and gallbladder. The trial showed that adding durvalumab, an immune checkpoint inhibitor, to standard gemcitabine-cisplatin chemotherapy improved overall survival compared with chemotherapy alone. That finding led to FDA approval and changed international treatment guidelines, but the survival benefit, the safety tradeoffs, and the economics of the regimen all deserve a closer look.
What TOPAZ-1 Tested
Advanced biliary tract cancer has historically been one of the harder cancers to treat. For roughly a decade before TOPAZ-1, the go-to regimen was gemcitabine plus cisplatin (often shortened to GemCis), a two-drug chemotherapy combination. Median survival on GemCis alone hovered around 11 months, and options after that regimen failed were limited.
TOPAZ-1 asked a straightforward question: does adding durvalumab to GemCis help patients live longer? Durvalumab is a PD-L1 inhibitor, meaning it blocks a protein that tumors use to hide from the immune system. The trial enrolled patients aged 18 and older who had unresectable, locally advanced, or metastatic biliary tract cancer that had not been previously treated with systemic therapy. Participants were randomly assigned in a 1:1 ratio to receive either durvalumab or a placebo alongside their GemCis chemotherapy.1The Lancet Gastroenterology & Hepatology. Updated overall survival and safety from TOPAZ-1
Chemotherapy was given for up to eight cycles. After that, patients continued on durvalumab or placebo alone until their disease progressed or side effects became intolerable.2PubMed. Durvalumab plus Gemcitabine and Cisplatin in Advanced Biliary Tract Cancer The trial was double-blind, so neither patients nor doctors knew who was getting the real drug, and it ran across 105 sites in 17 countries. Randomization was stratified by whether the cancer was initially unresectable versus recurrent, and by the primary tumor location: intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, or gallbladder cancer.3JAMA Oncology. Durvalumab Plus Chemotherapy for Advanced Biliary Tract Cancer: A Post Hoc Analysis of the TOPAZ-1 Randomized Clinical Trial
How Much Longer Did Patients Live
The trial’s primary endpoint was overall survival, and durvalumab met it. At an updated data cutoff, the median overall survival was about 12.9 months in the durvalumab group versus 11.3 months in the placebo group. That 1.6-month difference in medians may sound modest, but the hazard ratio tells a more complete story: patients on durvalumab had roughly a 24% lower risk of death at any given point during the study.4PubMed. Durvalumab or placebo plus gemcitabine and cisplatin in participants with advanced biliary tract cancer (TOPAZ-1): updated overall survival from a randomised phase 3 study
The gap between the two groups widened the further out you looked. At 24 months, about one in four patients on durvalumab was still alive, compared with roughly one in nine on placebo.5PubMed. Durvalumab or placebo plus gemcitabine and cisplatin in participants with advanced biliary tract cancer (TOPAZ-1): updated overall survival from a randomised phase 3 study By three years, a follow-up analysis with a median of about 41 months of tracking showed 36-month survival rates of roughly 15% with durvalumab versus 7% with placebo, and the hazard ratio tightened slightly to 0.74.6Journal of Hepatology. Durvalumab plus chemotherapy in advanced biliary tract cancer: 3-year overall survival update from the phase III TOPAZ-1 study In a cancer where almost nobody used to survive three years on chemotherapy alone, that tail on the survival curve is meaningful. It suggests a subset of patients derives a durable benefit from immunotherapy that standard chemo cannot provide.
Tumor Shrinkage and Progression-Free Survival
Beyond overall survival, the trial measured how well tumors responded and how long it took for the cancer to start growing again. The overall response rate was about 27% with durvalumab versus 19% with placebo, meaning tumors shrank by at least 30% in a larger proportion of patients receiving immunotherapy. Progression-free survival was also significantly better, with a hazard ratio of 0.75.7Journal of Clinical Oncology. A phase 3 randomized, double-blind, placebo-controlled study of durvalumab in combination with gemcitabine plus cisplatin (GemCis) in patients (pts) with advanced biliary tract cancer (BTC): TOPAZ-1
For patients who did respond, the durability of that response is what seemed to drive the longer-term survival advantage. The three-year data showing a widening gap between the arms supports the idea that durvalumab does not just delay progression for everyone by a small amount; rather, a fraction of patients responds well and maintains that benefit for a prolonged period. This “long-tail” effect is something oncologists have observed with checkpoint inhibitors across several cancer types, and TOPAZ-1 appears to follow that pattern.
Side Effects and Safety
One of the most practical questions for patients considering this regimen is whether adding an immunotherapy drug on top of already taxing chemotherapy makes the side effects meaningfully worse. In TOPAZ-1, the answer was largely no. Severe side effects (grade 3 or 4) occurred in about 74% of the durvalumab group and 75% of the placebo group, rates that were essentially identical. The most common serious side effects in both arms were drops in neutrophil counts and anemia, which are expected consequences of gemcitabine-cisplatin chemotherapy rather than effects of durvalumab itself.8The Lancet Gastroenterology & Hepatology. Updated overall survival and safety from TOPAZ-1
A pooled analysis comparing the safety profiles of both TOPAZ-1 and a similar trial called KEYNOTE-966 (which tested pembrolizumab instead of durvalumab) found that across more than 1,750 patients, the risk of most side effects did not significantly differ between the immunotherapy-plus-chemo arms and the chemo-alone arms.9PubMed. Safety evaluation of TOPAZ-1 and KEYNOTE-966 regimens in metastatic biliary tract cancer: a systematic review and meta-analysis That consistency across two large trials strengthens the case that the immunotherapy combination is tolerable for most patients.
Immune-Related Side Effects
Immune checkpoint inhibitors carry a unique category of side effects called immune-mediated adverse events, where the unleashed immune system mistakenly attacks healthy tissue. In TOPAZ-1, these were relatively uncommon. Hypothyroidism was the most frequent immune-related side effect, and all cases were mild. Serious immune-mediated events of grade 3 or 4 severity occurred in only about 2.4% of patients on durvalumab, compared with 1.5% on placebo. No deaths from immune-related events were reported in the durvalumab arm.10The Oncologist. Immune-mediated adverse events in the randomized phase 3 TOPAZ-1 study of durvalumab plus gemcitabine and cisplatin in advanced biliary tract cancer For a disease where patients are already managing the symptoms of their cancer alongside the burden of chemotherapy, this is a reassuring finding.
Did Patients Feel Any Different
Living longer only matters so much if the extra time comes at the cost of quality of life. TOPAZ-1 formally assessed patient-reported outcomes, tracking how participants rated their overall health, daily functioning, and symptom burden throughout treatment. There was no meaningful difference between the two groups on any of these measures. The median time before patients reported a decline in their quality of life was about 7.4 months in the durvalumab group versus 6.7 months in the placebo group, a gap that was not statistically significant.11PubMed. Durvalumab plus gemcitabine and cisplatin in advanced biliary tract cancer (TOPAZ-1): patient-reported outcomes from a randomised, double-blind, placebo-controlled, phase 3 trial
The takeaway is that durvalumab did not make patients feel worse. It added a survival benefit on top of chemotherapy without adding a detectable burden on how patients experienced their day-to-day lives. In oncology trials, that combination of improved survival with preserved quality of life is the ideal outcome, and it does not always happen.
Results Across Different Tumor Locations
Biliary tract cancer is not one disease. It includes intrahepatic cholangiocarcinoma (tumors inside the liver), extrahepatic cholangiocarcinoma (tumors in the bile ducts outside the liver), and gallbladder cancer. These subtypes behave differently and can respond differently to treatment, so an important question was whether durvalumab helped across all of them.
A subgroup analysis found that the survival benefit held across all three tumor locations, though the magnitude varied. For intrahepatic and extrahepatic cholangiocarcinoma, the survival hazard ratios favored durvalumab at 0.76 and 0.76, respectively. Gallbladder cancer showed a smaller benefit, with a hazard ratio of 0.94. The progression-free survival advantage was particularly pronounced in extrahepatic cholangiocarcinoma, where the hazard ratio was 0.52, meaning patients had roughly half the risk of their cancer worsening compared with placebo.12Journal of Oncology Navigation & Survivorship. TOPAZ-1 Trial Subanalysis: Outcomes by Primary Tumor Location in Advanced BTCs The overall response rates also favored durvalumab across all three subtypes, though gallbladder cancer showed the smallest difference.
These findings matter because gallbladder cancer in particular had limited evidence for immunotherapy. While the benefit signal was weaker there, it was still present, and the trial authors concluded that durvalumab plus GemCis is a reasonable option regardless of where the primary tumor sits.
Geographic and Demographic Patterns
Biliary tract cancers are more common in parts of East and Southeast Asia than in Western countries, partly due to higher rates of liver fluke infections and chronic hepatitis B. TOPAZ-1 enrolled about 55% of its participants from Asia and 45% from the rest of the world, giving researchers enough data to look at whether geography affected outcomes.
Regional analysis showed that outcomes generally tracked with the overall trial results across Asia, Europe, and North America. The survival benefit of adding durvalumab appeared somewhat stronger in Asian participants than in those from other regions. Interestingly, despite a higher prevalence of hepatitis B in the Asian cohort, survival outcomes were similar in patients with and without viral hepatitis.13Journal of Clinical Oncology. Regional subgroup analysis of the phase 3 TOPAZ-1 study of durvalumab (D) plus gemcitabine and cisplatin (GC) in advanced biliary tract cancer (BTC) South America was the one region where the placebo arm performed better, though the small sample size from that region makes it hard to draw firm conclusions. The grade 3 or 4 adverse event rates were also comparable between Asian and non-Asian participants, suggesting the safety profile holds up across populations.
How It Performs Outside of Clinical Trials
Clinical trial populations are carefully selected. Patients tend to be healthier, better monitored, and more adherent to treatment schedules than the broader population. So a key test for any new regimen is whether the trial results hold up in everyday clinical practice.
Early real-world data has been encouraging. A UK study that tracked 133 patients who received durvalumab plus GemCis through an early access program found a median progression-free survival of about 8.8 months and a median overall survival of 12 months. The response rate was roughly 29%, closely matching the trial’s figure. Side effects were actually milder than in TOPAZ-1, with grade 3 or 4 events occurring in only about 7% of patients, compared with 74% in the trial. That discrepancy likely reflects differences in how adverse events are recorded in routine practice versus a tightly monitored trial setting.14PubMed Central. UK Real-World Evidence of Using Durvalumab Plus Cisplatin and Gemcitabine in Advanced Biliary Tract Cancer via an Early Access Scheme
A smaller multicenter cohort study of 45 patients reported a median overall survival of about 15.8 months, actually exceeding the trial result. The response rate was 31%, with an additional 40% of patients achieving stable disease. Patients whose tumors responded to treatment survived significantly longer than those whose tumors did not, which aligns with the trial’s “long-tail” pattern.15PubMed Central. Real-world effectiveness and prognostic factors of durvalumab plus chemotherapy in a multicentric cohort with advanced biliary tract cancer These real-world cohorts are still small, and follow-up periods are relatively short, but so far the effectiveness of the regimen appears to translate outside of the controlled trial environment.
Regulatory Approval and Guideline Changes
On the strength of the TOPAZ-1 results, the US FDA approved durvalumab in combination with gemcitabine and cisplatin for locally advanced or metastatic biliary tract cancer. The NCCN (National Comprehensive Cancer Network) guidelines now recommend this combination as a preferred first-line regimen for patients with metastatic, locally advanced, or unresectable disease.16PubMed Central. Recent advancements in systemic therapy for biliary tract cancers: a literature review A separate trial called KEYNOTE-966, which tested pembrolizumab (a different checkpoint inhibitor) with GemCis, produced similar results, meaning two immunotherapy-plus-chemo options are now available as standard care. A pooled analysis of both trials, involving over 1,750 patients, confirmed the survival advantage of adding checkpoint inhibitors to chemotherapy.17PubMed Central. Systemic Therapy for Advanced Biliary Tract Cancers in 2026: Current Standard of Care and Emerging Therapeutic Strategies
This matters because biliary tract cancer had been a treatment landscape with remarkably few advances. The same chemotherapy backbone had been the default for roughly a decade. Having two validated immunotherapy partners gives oncologists and patients some choice, and it has opened the door for research into second-line immunotherapy options and targeted therapies after the first-line combination stops working.
The Cost Problem
The clinical case for adding durvalumab is relatively clear. The economic case is not. Health economic analyses based on the TOPAZ-1 data have consistently found that the regimen is expensive relative to the survival benefit it provides. A cost-effectiveness analysis from the Chinese healthcare perspective estimated that adding durvalumab to chemotherapy produced an additional 0.12 quality-adjusted life years (roughly six extra weeks of life in full health) at a cost that translated to an incremental cost-effectiveness ratio well above standard willingness-to-pay thresholds, even with charitable drug assistance programs factored in. The analysis found that durvalumab’s price would need to drop by more than 94% to become cost-effective in that setting.18PubMed Central. Cost-effectiveness analysis of adding durvalumab to chemotherapy as first-line treatment for advanced biliary tract cancer based on the TOPAZ-1 trial
From a US payer perspective, the picture is similarly stark. A trial-based economic evaluation estimated an incremental cost of about $131,000 for an additional 0.26 quality-adjusted life years, yielding a cost per QALY gained of roughly $505,000.19Journal of Clinical Oncology. Economic evaluation for the US of durvalumab plus gemcitabine and cisplatin (DGC) in advanced biliary tract cancer (BTC) For reference, many health systems use thresholds of $100,000 to $150,000 per QALY as a benchmark for acceptable value. These numbers exceed that range by a wide margin.
This does not mean the treatment is not worthwhile for individual patients. It means that at current drug pricing, health systems face genuine tension between offering a clinically proven regimen and managing constrained budgets. It is a common story in oncology, where immunotherapy drugs often provide real but incremental survival gains at high sticker prices. For patients in countries without universal coverage or robust insurance, access can be a serious barrier even when the drug is approved.
What Remains Unknown
TOPAZ-1 answered the big question about whether immunotherapy belongs in first-line biliary tract cancer treatment. Several smaller questions remain open. There is still no reliable biomarker to predict which patients will be the long-term survivors. Unlike in some other cancers, PD-L1 expression levels in biliary tract cancer have not clearly separated responders from non-responders, which means the treatment is currently offered broadly rather than to a selected subgroup most likely to benefit. Research into tumor mutational burden, microsatellite instability, and other molecular features is ongoing but has not yet produced a marker that could guide patient selection with confidence.
There is also limited data on what to do after durvalumab-plus-GemCis stops working. The original standard of care after first-line GemCis failure was a different chemotherapy agent, but it is unclear whether that approach still works as well in patients whose tumors have already been exposed to immunotherapy. Second-line trials in this space are underway, and their results will fill an important gap for patients who progress on the TOPAZ-1 regimen.