Managements for refractory proficient mismatch repair (pMMR) or microsatellite stable (MSS) metastatic colorectal cancer (mCRC) were still challenging and controversial. Our study sought to investigate the efficacy and safety of anti-PD-1 antibodies plus regorafenib in refractory pMMR/MSS mCRC between July 2019 and June 2021 at the Hunan Cancer Hospital.

We retrospectively analyzed the efficacy and safety of 103 pMMR/MSS mCRC patients treated with at least one dose of anti-PD-1 antibodies plus regorafenib (80 mg once daily for 21 days on/7 days off 28 days as a cycle) between July 2019 and June 2021 at the Hunan Cancer Hospital. All patients had previously received at least second-line treatment. The patients were evaluated by computed tomography every 2 or 3 treatment cycles until progression or being lost to follow-up. The primary end point was overall survival (OS).

Inclusion Criteria:

• Inclusion Criteria:

• 1.Has histologically confirmed unresectable adenocarcinoma of the colon or rectum (all other histological types are excluded).

  2. Have progressed from at least 2 lines of standard treatment,including fluoropyrimidines, irinotecan, oxaliplatin, with or without targeted drugs, like bevacizumab and cetuximab (only for RAS wild-type).

  3.Has measurable or non-measurable disease as defined by RECIST version 1.1 4.Is able to swallow oral tablets. 5.Estimated life expectancy ≥12 weeks. 6.Eastern Cooperative Oncology Group performance status (ECOG PS) 0 or 1 7. Has adequate organ function.

Exclusion Criteria:

• 1.Pregnancy, lactating female or possibility of becoming pregnant during the study.

  2.Has not recovered from clinically relevant non-hematologic CTCAE grade ≥ 3 toxicity of previous anticancer therapy (excluding alopecia, and skin pigmentation).

  3.Has symptomatic central nervous system metastases that are neurologically unstable or requiring increasing doses of steroids to control CNS disease.

  4.Has severe or uncontrolled active acute or chronic infection. 5.Known carriers of HIV antibodies. 6.Confirmed uncontrolled arterial hypertension or uncontrolled or symptomatic arrhythmia.

Study population were the patients treated with at least 1 cycle of anti-PD-1 antibodies plus regorafenib between July 2019 and June 2021 at the Hunan Cancer Hospital.

De-identified participant data from the final research dataset used in the published manuscript may only be shared under the terms of a Data Use Agreement. Requests may be directed to: [contact information for principal investigator or correspondence author]. The protocol and statistical analysis plan will be made available on Clinicaltrials.gov only as required by federal regulation or as a condition of awards and agreements supporting the research.

Data can be shared no earlier than 1 year following the date of publication

please contact the principal investigator of this study or correspondence author.