Summary

This phase II/III trial compares the effect of adding radiation therapy to the usual maintenance therapy with atezolizumab versus atezolizumab alone in patients who have already received atezolizumab plus chemotherapy for the treatment of small cell lung cancer that has spread outside of the lung or to other parts of the body (extensive stage). Immunotherapy with monoclonal antibodies, such as atezolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. Giving radiation therapy in addition to atezolizumab may extend the time without extensive small cell lung cancer growing or spreading compared to atezolizumab alone.

Objectives

PRIMARY OBJECTIVES:
I. To compare investigator-assessed progression free survival (PFS) between atezolizumab plus radiotherapy and atezolizumab alone. (Phase II)
II. To compare overall survival (OS) between atezolizumab plus radiotherapy and atezolizumab alone. (Phase III)

SECONDARY OBJECTIVES:
I. To assess the toxicity between the atezolizumab plus radiotherapy arm and the atezolizumab arm.
II. To assess the impact of adding radiotherapy on PFS and OS in patients with 1-3 visible tumors and > 3 visible tumors.
III. To assess the impact of adding radiotherapy on PFS and OS in patients receiving consolidation radiotherapy to all visible disease (“complete consolidation”) and patients who do not receive consolidation radiation to all visible disease (“incomplete consolidation”).

EXPLORATORY OBJECTIVE:
I. To assess the association between pre-treatment tumor burden (determined by central radiographic assessment, using both tumor number and tumor volume), and PFS and OS benefit.

OUTLINE: Patients are randomized to 1 of 2 arms.

ARM I: Patients receive atezolizumab intravenously (IV) over 30 minutes +/- 10 minutes on day 1. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.

ARM II: Patients receive atezolizumab IV over 30 minutes +/- 10 minutes. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity. Patients undergo radiation therapy once daily (QD) on days 1-5 during weeks 1-5 only.

Patients undergo positron emission tomography and computed tomography (PET/CT) scan, computed tomography (CT), and magnetic resonance imaging (MRI) throughout the trial. Patients also undergo blood and tissue collection throughout the trial.

After completion of study treatment, patients are followed up every 3 months for 2 years, every 6 months for 3 years, and then annually thereafter.