Evaluation of the relationship between tumor PD-l1 and peritumoral cd8 + til levels in primary or metastatic tissue with response to chemotherapy and survival in metastatic colorectal cancer patients receiving bevacizumab or cetuximab

In this study, PD-L1 expression and TIL levels in primary or metastatic tissues in patients will be evaluated immunohistochemically and their relationship with chemotherapy and survival will be investigated. Patients between the ages of 18 and 80, who were diagnosed with metastatic colorectal cancer and who received treatment with Bevacizumab or Cetuximab in addition to chemotherapy in the first-line treatment were accepted. Pathology samples of patients were stained in the Department of Pathology by the immunohistochemistry method. The patients included in the study were divided into two groups as chemotherapy + Bevacizumab or chemotherapy + Cetuximab. The mean age of patients in the first group (chemotherapy + Bevacizumab) was 60.42 ± 11.968 years, and the mean age of patients in the second group (chemotherapy + Cetuximab) was 58.30 ± 10.49 years. The median progression-free survival time was 15 months in both groups. Response rates to chemotherapy were similar in both groups, in the first group, 1 patient (2.8%) had a complete response, 27 patients (75.0%) had partial response, and 8 patients (22.2%) had progression. In the second group, 5 patients (15.2%) partial response was observed in 22 patients (66.7%) and progression in 6 patients (18.2%). As a result of the IHC assessment, in the first group CD8 + TIL expression was low in 9 patients (25.0%) and high in 27 patients (75.0%), while in the second group low in 11 patients (33,3%) and high in 22 patients (66,7%) peritumoral CD8 + TIL expression was observed. Statistically significant relationship was not found between high and low peritumoral CD8 + TIL levels and PFS in both groups (p = 0.918 in the first group, p = 0.184 in the second group). Also, there was no relationship between Peritumoral CD8 + TIL levels and chemotherapy response in both groups (p = 0.546 in the first group, p = 1.000 in the second group). As a result of the IHC assessment, 28 patients (77.8%) did not have PD-L1 expression in the first group, while 6 patients (16.7%) had low-intermediate PD-L1 expression and 2 patients (5.6%) had high PD-L1 vii expression. In the second group, PD-L1 expression was not observed in 30 patients (90.0%), while low-intermediate PD-L1 expression was observed in 3 patients (9.1%) and no high PD-L1 expression was observed. In the first group (chemotherapy + Bevacizumab), there was no statistically significant relationship between tumoral PD- L1 expression and PFS (p = 0.436), whereas, in the second group (chemotherapy + Cetuximab), the presence of PD-L1 expression was associated with shorter PFS (16 months and 6 months, p < 0,001). In the first group, there was no statistically significant relationship between tumoral PD-L1 expression and chemotherapy response (p = 0.149), but in the second group, there was a statistically borderline correlation between tumoral PD-L1 expression and response to chemotherapy (p = 0.070). In conclusion, we showed that concurrent use of cetuximab to chemotherapy was associated with shorter PFS and worse response to chemotherapy in PD-L1 expression in patients with stage IV colorectal cancer. We believe that simultaneous treatment with chemotherapy may be more effective in this group of patients.