RECIST 1.1, Choi and mChoi criteria in the evaluation of tumor response in patients with metastatic colorectal cancer treated with Regorafenib and anti-PD-1 antibody.

Purpose: No comparative study on evaluating performance of radiological criteria has been investigated in metastatic colorectal cancer (mCRC) patients treated with the combination of Regorafenib and anti-programmed cell death 1(PD-1) antibody. We aimed to compare the performance of different radiological criteria in evaluating response in mCRC patients treated with the combination of Regorafenib plus anti-PD-1 antibody.

Method: We retrospectively recruited patients treated with Regorafenib and anti-PD-1 antibody in a single institution. Baseline and the first tumor evaluation of contrast-enhanced computed tomography (CE-CT) were assessed by three evaluation criteria: RECIST 1.1, Choi, modified Choi (mChoi). Overall survival (OS) was defined as endpoint event.

Results: Twenty-three mCRC patients [age: 58.8 ± 10.6 years, 18 (78.3 %) males] were assessed. The median overall survival was 11.8 months. According to RECIST 1.1, 8 (34.8 %) patients were stable disease (SD) and 15 (65.2 %) were progressive disease (PD). According to Choi and mChoi, 5 (21.7 %) and 1(4.3 %) patient was responders, respectively. All non-PD patients showed significantly better overall survival than PD patients by all criteria. According to Choi, those identified as responders showed better overall survival than non-responders though significant statistics were not reached (P=0.262).

Conclusions: RECIST 1.1, Choi and mChoi criteria could identify survival benefit from Regorafenib plus anti-PD-1 antibody in mCRC patients. However, the value of responders detected by Choi remains to be validated in further studies.