Pilot evaluation of PD-1 inhibition in metastatic cancer patients with a history of liver transplantation: the Mayo Clinic experience

Abstract

Background: Patients with solid organ transplants (SOTs) have been excluded from programmed death protein-1 (PD-1)/programmed death ligand-1 (PD-L1) inhibitor clinical trials due to concern for allograft rejection. The use of immune checkpoint inhibitor therapy remains controversial in transplant patients.

Methods: A retrospective pilot evaluation was conducted to assess the safety and efficacy of PD-1 inhibitors in patients with liver transplantation (LT). The primary endpoint was the rate of allograft rejection. Secondary endpoints included overall response rate (ORR), progression free survival (PFS) and overall survival (OS). Translational objectives included evaluation of tumor PD-L1, tumor infiltrating lymphocytes (TILs) and allograft PD-L1 expression.

Results: Seven metastatic cancer patients with a history of LT who received PD-1 inhibitor therapy were included [hepatocellular carcinoma (HCC), n=5; melanoma, n=2]. Rejection was observed in 2 of 7 patients. When rejection occurs it appears to be an early event with a median time to rejection of 24 days in our cohort. One patient achieved a complete response (CR), 3 patients had progressive disease (PD) and 3 patients discontinued therapy prior to restaging assessments. Two of five patients with available tissue had PD-L1 expression in the allograft and both developed rejection. One of five evaluable patients had abundant TILs. Two of five evaluable patients had PD-L1 tumor staining. The single patient with both abundant TILs and PD-L1 staining obtained a response. The median OS and PFS were 1.1 (0.3-21.1) and 1.8 (0.7-21.1) months, respectively.

Conclusions: In this pilot evaluation both preliminary efficacy (1 of 4) and allograft rejection (2 of 7) were exhibited in evaluable patients. Larger, prospective trials are needed to elucidate optimal patient selection.

Keywords: Immunotherapy; graft rejection; hepatocellular carcinoma (HCC); liver transplantation (LT); melanoma.

Figure 1

PET/CT scans of patient #2. (A) PET/CT prior to immunotherapy in patient #2; (B) PET/CT scan showing radiographic complete response in patient #2 after completing pembrolizumab treatment.

Figure 2

PD-L1 immunohistochemistry in liver allograft tissue near the portal vein in patient #6 (A) (magnification ×100) and patient #7 (B) (magnification ×200). Brown staining represents PD-L1 expression in portal lymphocytes. Image (B) shows enrichment of PD-L1 lymphocyte staining in areas of endotheliitis. *, denotes the portal vein. PD-L1, programmed death ligand-1.