SUMMARY: The American Cancer Society estimates that for 2024 about 234,580 new cases of lung cancer will be diagnosed and about 125,070 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Small Cell Lung Cancer (SCLC) accounts for approximately 13-15% of all lung cancers and is aggressive. Limited Stage-Small Cell Lung Cancer – LS-SCLC (Stage I-III) accounts for approximately 30% of SCLC diagnoses and the disease is confined to one hemithorax. These patients are often treated with a combination of Carboplatin or Cisplatin with Etoposide and radiotherapy. Despite initial response, LS-SCLC typically recurs and progresses rapidly, and only 15-30% of patients are alive, five years after diagnosis.
Based on the premise that SCLC has a high mutation rate, it was hypothesized that these tumors may be immunogenic, and more recently immunotherapy with checkpoint inhibitors has demonstrated clinical activity in SCLC. Durvalumab (IMFINZI®) is a selective, high-affinity, human IgG1 monoclonal antibody, that blocks the binding of Programmed Death Ligand 1 (PD-L1) to Programmed Death 1 (PD-1) receptor and CD80, thereby unleashing the T cells to recognize and kill tumor cells. Tremelimumab (IMJUDO®) is a human immunoglobulin G2 monoclonal antibody that targets and blocks the activity of CTLA-4, enhancing binding of CD80 and CD86 to CD28. This complimentary mechanisms of action broadens clinical activity, potentially overcoming primary resistance to PD-(L)1 blockade by enabling novel T-cell responses.
The rationale for the ADRIATIC trial was supported by findings from the pivotal Phase III PACIFIC and CASPIAN trial. In the PACIFIC trial, Durvalumab after concurrent chemoradiotherapy for Stage III Non-Small Cell Lung Cancer, improved both Overall Survival (OS) and Progression Free Survival (PFS), whereas in the CASPIAN trial, Durvalumab with Platinum and Etoposide chemotherapy significantly improved OS, compared to chemotherapy alone, in newly diagnosed patients with extensive-stage SCLC.
The ADRIATIC trial is a Phase III, randomized, double-blind, placebo-controlled, multicenter, global study that assessed the efficacy and safety of Durvalumab as consolidation therapy in patients with Limited-Stage Small Cell Lung Cancer (LS-SCLC) who had not progressed after concurrent platinum-based chemoradiotherapy. This trial randomized 730 patients with Stage I to III LS-SCLC, including those with inoperable Stage I/II disease. Eligible patients had a WHO Performance Status of 0 or 1 and had not experienced disease progression after completing concurrent chemoradiotherapy. Chemotherapy consisted of a combination of Platinum plus Etoposide for up to 4 cycles, and the radiation therapy could either be once daily up to 66 Gy, or twice a day up to 45 Gy. Prophylactic Cranial Irradiation (PCI) was allowed before randomization. Patients were randomized within 6 weeks after completing concurrent chemoradiotherapy to experimental arms Durvalumab monotherapy 1500 mg IV every 4 weeks with or without Tremelimumab 75 mg IV every 4 weeks for up to 4 cycles each, followed by Durvalumab every four weeks for up to 24 months or Placebo every 4 weeks. There was a protocol amendment in November 2020, and patients were randomly assigned in a 1:1 ratio to the Durvalumab group or placebo group only. Baseline characteristics and prior treatment were well balanced between groups. The median age was 62 years and 87% of patients had Stage III disease at diagnosis. This analysis compared the outcomes in patients assigned to receive Durvalumab monotherapy (N=264) with patients who received placebo (N=266). The dual Primary endpoints were Progression Free Survival (PFS) and Overall Survival (OS) for Durvalumab monotherapy versus placebo. Key Secondary endpoints included OS and PFS for Durvalumab plus Tremelimumab versus placebo, Safety, and Quality of Life measures. The median duration of follow-up for OS and PFS in censored patients at this first planned interim analysis was 37.2 and 27.6 months, respectively.
Durvalumab demonstrated a statistically significant improvement in OS compared to placebo (HR=0.73; P=0.01), translating to a 27% reduction in the risk of death. The estimated median OS with Durvalumab was 55.9 months, compared to 33.4 months with placebo. The 24-month OS rate was 68% with Durvalumab versus 58.5% with placebo, and the 36-month OS rate was 56.5% versus 47.6%, respectively. The median PFS was 16.6 months with Durvalumab versus 9.2 months with placebo, representing a 24% reduction in the risk of disease progression or death (HR=0.76; P=0.02). The 18-month PFS rate was 48.8% with Durvalumab versus 36.1% with placebo, and the 24-month PFS rate was 46.2% with Durvalumab versus 34.2% with placebo. Treatment benefit was generally consistent across predefined patient subgroups for both OS and PFS. Grade 3/4 Adverse Events (AEs) were similar in both treatment groups at 24.3%, but treatment discontinuation due to AEs was slightly higher in the Durvalumab arm (16.3% versus 10.6% in the placebo arm). Any grade pneumonitis was reported in 38.0% of patients in the Durvalumab arm compared to 30.2% in the placebo arm.
The results of the ADRIATIC trial represent a significant advancement in the treatment of Limited Stage-Small Cell Lung Cancer (LS-SCLC). Durvalumab consolidation therapy demonstrated a statistically significant and clinically meaningful improvement in both OS and PFS compared to placebo. These findings support Durvalumab as a new standard of care for patients with LS-SCLC following concurrent chemoradiotherapy, potentially changing the treatment landscape for this aggressive disease.
Durvalumab after Chemoradiotherapy in Limited-Stage Small-Cell Lung Cancer. Cheng Y, Spigel DR, Cho BC, et al. for the ADRIATIC Investigators. N Engl J Med 2024;391:1313-1327.
