Cancer of unknown primary has a dismal prognosis, especially following failure of platinum-based chemotherapy. 10-20% of patients have a high tumor mutational burden (TMB), which predicts response to immunotherapy in many cancer types. In this prospective, non-randomized, open-label, multicenter Phase II trial (EudraCT 2018-004562-33; NCT04131621), patients relapsed or refractory after platinum-based chemotherapy received nivolumab and ipilimumab following TMB high vs. TMB low stratification. Progression-free survival (PFS) represented the primary endpoint; overall survival (OS), response rates, duration of clinical benefit and safety were the secondary endpoints. The trial was prematurely terminated in March 2021 before reaching the preplanned sample size ( n = 194). Among 31 evaluable patients, 16% had a high TMB ( > 12 mutations/Mb). Overall response rate was 16% (95% CI 6-34%), with 7.7% (95% CI 1-25%) vs. 60% (95% CI 15-95%) in TMB low and TMB high , respectively. Although the primary endpoint was not met, high TMB was associated with better median PFS (18.3 vs. 2.4 months) and OS (18.3 vs. 3.6 months). Severe immune-related adverse events were reported in 29% of cases. Assessing on-treatment dynamics of circulating tumor DNA using combined targeted hotspot mutation and shallow whole genome sequencing as part of a predefined exploratory analysis identified patients benefiting from immunotherapy irrespective of initial radiologic response.

Following the PACIFIC trial, durvalumab has been approved by the European Medicines Agency (EMA) for consolidation of locally advanced PD-L1-positive NSCLC after chemoradiotherapy (CRT). Patients were treated with durvalumab in the EAP from 22.11.2017 to 15.10.2018 allowing analysis of its efficacy and safety. 211 patients were registered by 90 German centres. Data were collected retrospectively by questionnaire and queries. 56 centres reported data on 126 patients who actually received at least one cycle of durvalumab. In contrast to the PACIFIC-trial population, some patients with oligometastatic disease and a history of autoimmune disease are included in the EAP population. Information on PD-L1 status was obtained for 111 patients. Baseline data include age, gender, ECOG, stage (IASLC 8th ed.), and smoking history. Treatment data include mode of chemoradiotherapy, used chemotherapy agent, and duration of durvalumab therapy. Adverse evants were documented according to CTAEC 5.0. Data were analysed for progression-free survival (PFS), overall survival (OS), and adverse events (AE). The results were published in Lung Cancer [1].