Clinical outcomes and histologic findings in patients with durable PR or SD with atezolizumab-bevacizumab for hepatocellular carcinoma

Durable partial response and durable stable disease (PR/SD; durable defined as lasting more than 6 months) are often seen in patients with hepatocellular carcinoma (HCC) receiving atezolizumab plus bevacizumab (atezo-bev). In the IMbrave150 trial, 77.8% of the PRs and 28.5% of the SDs were durable. The median overall survival was not estimable for patients with durable PR and 23.7 months for those with durable SD, while the median progression-free survival was 23.2 months for patients with durable PR and 13.2 months for patients with durable SD. In a real-world study at eight centers in Japan and eight centers in Taiwan, 38 residual tumors were resected from 32 patients (23 PR and 9 SD) having received atezo-bev for HCC. Pathologic complete response (pCR) was more frequent in PR tumors than in SD tumors (57.7% versus 16.7%; p=0,034). pCR rate correlated with time for atezo-bev initiation to resection, and was 55.6% for PR tumors resected beyond 8 months after starting atezo-bev. Around half of durable PR tumors where ‘ghost tumors’; radiologically persistent tumors without viable cancer cells. The authors conclude that the prevalence of ghost tumors may help explain the longer overall survival in patients with durable PR and in certain patients with durable SD in the atezo-bev group in IMbrave150.