Atezolizumab and Bevacizumab in Treating Patients With Rare Solid Tumors

PRIMARY OBJECTIVES: I. To evaluate the efficacy of atezolizumab when given in combination with bevacizumab (atezo bev). SECONDARY OBJECTIVES: I. To evaluate the efficacy of atezo bev. II. To evaluate the safety of atezo + bev. EXPLORATORY BIOMARKER OBJECTIVES: I. To identify biomarkers that are predictive of response to atezo bev (i.e., predictive biomarkers), are associated with progression to a more severe disease state (i.e., prognostic biomarkers), are associated with resistance to atezo bev, are associated with susceptibility to developing adverse events, can provide evidence of study treatment activity, or can increase the knowledge and understanding of disease biology. OUTLINE: Patients receive atezolizumab and bevacizumab intravenously (IV) over 60 minutes on day 1. Courses repeat every 21 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months.