Efficacy Outcomes in the IMforte Trial: PFS, OS, and Clinical Impact

Stephen Liu, MD Georgetown Lombardi Comprehensive Cancer Center | Rahul Gosain, MD, MBA Wilmot Cancer Institute | Rohit Gosain, MD Roswell Park Comprehensive Cancer Center

October 11, 2025

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Key Points

  • The phase 3 IMforte trial on extensive-stage small cell lung cancer (ES-SCLC) moved lurbinectedin up from the second-line setting into the first line as a maintenance therapy.

  • Maintenance with lurbinectedin plus atezolizumab improved overall survival (OS) and progression-free survival (PFS) versus atezolizumab alone after induction therapy.

Lurbinectedin Plus Atezolizumab Shows Improved Median OS

The IMforte trial updated the first-line standard of care for untreated ES-SCLC to include maintenance therapy with lurbinectedin plus atezolizumab after induction therapy with carboplatin, etoposide, and atezolizumab. One of the authors of the study, Stephen Liu, MD, of Georgetown Lombardi Cancer Center, shared findings from IMforte during a roundtable discussion on the Oncology Brothers podcast.

Lurbinectedin has been used to treat ES-SCLC in the second-line setting for years. When bringing any active drug into an earlier treatment line, the expectation is more responses, improved PFS, and more toxicity, with the ultimate goal being to improve OS, said Dr. Liu.

In IMforte, lurbinectedin plus atezolizumab yielded a median OS from randomization of 13.2 months versus 10.6 months with atezolizumab only (stratified hazard ratio [HR], 0.73; 95% CI, 0.57–0.95; P = .017). The 1-year rate of OS was 56% with the lurbinectedin combination compared with 44% with atezolizumab alone. Additionally, lurbinectedin plus atezolizumab yielded a PFS of 5.4 months versus 2.1 months with atezolizumab alone (stratified HR, 0.54; 95% CI, 0.43–0.67; P < .0001). 

Treatment with lurbinectedin was associated with more toxicities including nausea, fatigue, anemia, and neutropenia, but most events were low grade and only 6% of patients stopped any part of treatment due to toxicity, Dr. Liu said. Most adverse events occurred within the first 9 weeks of maintenance therapy, and dose interruptions were mostly driven by hematologic toxicities, he added.