DeLLphi-305: what the 58% survival figure really means for SCLC

Amgen presented late-breaking Phase 3 DeLLphi-305 results at the European Society for Medical Oncology Congress in Madrid on Oct. 24, 2026, and published them the same day in The New England Journal of Medicine. The trial tested IMDELLTRA (tarlatamab-dlle) plus AstraZeneca's IMFINZI (durvalumab) as first-line maintenance therapy in patients with extensive-stage small cell lung cancer whose disease had not progressed after four cycles of induction chemotherapy and immunotherapy.

The combination reduced the risk of death by 58% versus IMFINZI alone, with a hazard ratio of 0.42 and a 95% confidence interval of 0.32 to 0.54 (P < 0.001) at a median follow-up of approximately 16 months. Median overall survival was 21.1 months versus 12.7 months — an 8.4-month gain. Nearly 80% of patients were alive at one year versus 53% with IMFINZI alone, and progression-free survival more than tripled. The benefit extended to subgroups including patients with brain metastases and liver metastases.

That 58% is a relative risk reduction, not an absolute one. It describes how much the hazard of death fell compared with durvalumab alone in this specific maintenance population. It does not mean 58% of patients were cured, and it does not apply to all lung cancers. The absolute figure — 8.4 additional median months — is the number a patient and clinician would weigh against side effects and cost.

Amgen announced on Sept. 8 that the trial had met its survival goal but held the figures for the ESMO Presidential Symposium. Amgen chief medical officer Paul Burton called the result a "watershed moment" and "unprecedented" for the field. Those are the sponsor's characterizations, not independent findings.

Extensive-stage small cell lung cancer is fast-growing and has spread beyond the lung, with historically poor survival. Durvalumab is the current standard of care after chemotherapy for patients whose cancer does not worsen after initial treatment. If approved in this maintenance setting, the tarlatamab-durvalumab combination could shift that standard.

Serious side effects and treatment costs remain open concerns. The sources do not specify which serious adverse events occurred or at what rates, what the combination will cost, whether insurers will cover it, or when Amgen will file for regulatory approval. The durability of the survival benefit beyond roughly 16 months of median follow-up is also unknown.

What the trial shows is a statistically robust survival improvement in a defined group of patients. What it does not show is a cure, a general lung cancer treatment, or an answer to the questions about toxicity, price, and access that will determine how far the benefit reaches in practice.