Response to atezolizumab plus bevacizumab specific for lung and lymph node metastases affects survival of patients with HCC

Background & Aims: Tumour microenvironment heterogeneity among different organs can influence immunotherapy responses. Here, we evaluated the impact of differential organ-specific responses on survival in patients with advanced-stage hepatocellular carcinoma (HCC) treated with atezolizumab plus bevacizumab (Atezo/Bev). Methods: We retrospectively analysed 366 consecutive patients with advanced-stage HCC treated with Atezo/Bev as first-line systemic treatment. Therapeutic response was assessed using RECIST v1.1. Patients were divided into an intention-to-treat (ITT) group (patients treated with >= 1 dose of Atezo/Bev) and a per-protocol (PP) analysis group (patients with at least one measurable lesion irrespective of location treated with >= 3 doses of Atezo/Bev). Overall response and organ-specific response at initial and best response were evaluated in the PP group. Responders were defined as patients achieving complete remission or partial response. Initial progressors were defined as patients with progressive disease after three doses of Atezo/Bev. Results: The ITT and PP groups comprised 324 and 236 patients, respectively. In the PP group, the organ-specific response rate of lung and lymph node (LN) metastases at both initial and best responses were higher than those of intrahepatic lesions and macrovascular tumour thrombosis. Lung and LN-specific response rates were 21.1% and 23.5%, respectively, at initial response, and 24.7% and 31.4%, respectively, at best response. Both initial pulmonary and lymphatic progressors (adjusted hazard ratios [95% confidence intervals], 6.37 [2.10-19.3], and 8.36 [2.16-32.4], respectively) were independently associated with survival regardless of intrahepatic response. Conclusions: The response of metastatic HCC to the Atezo/Bev regimen may be used to determine whether to continue treatment or switch to second-line treatment at an early phase of therapy.