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Value of PD-L1, PD-1, and CTLA-4 Expression in the Clinical Practice as Predictors of Response to Nivolumab and Ipilimumab in Monotherapy in Patients With Advanced Stage Melanoma.

BACKGROUND
The introduction of immune checkpoint inhibitors (ICI) has improved the survival outcomes of patients with advanced melanoma. To date, only a few studies have evaluated the immunohistochemical (IHC) expression of PD-1 and CTLA-4 in tumor-infiltrating lymphocytes (TILs) as predictive markers of response to ICI, most of them in the context of clinical trials. Moreover, the predictive value of PD-L1 in melanoma cells in the response to immunotherapy is unclear. The aim of our study was to assess the IHC expression of PD-L1, PD-1, and CTLA-4 in samples of patients with advanced melanoma and to establish their prognostic value as predictors of ICI response in a university hospital.


METHODS
The expression of PD-L1, PD-1, and CTLA-4 was evaluated in pretreatment tumor samples in a series of 35 patients, 21 patients treated with nivolumab and 14 patients with ipilimumab in monotherapy.


RESULTS
In the nivolumab group, 4 tumors (19%) were positive for PD-L1 and all of them showed a partial response to the treatment. However, 4 patients whose tumors did not express PD-L1 also responded to nivolumab. PD-1 expression was not associated with better progression-free survival (PFS). In the ipilimumab group, 5 patients (35.7%) showed expression of CTLA-4. Positive cases showed a better PFS; however, one negative case responded to ipilimumab.


CONCLUSIONS
Nivolumab produces a better response compared with ipilimumab in patients with melanoma. The IHC expression of PD-L1 and CTLA-4 are associated with a higher response rate to nivolumab and ipilimumab, respectively, and better PFS, but the existence of responder patients with negative expression suggests that they are not adequate biomarkers to select candidate patients for ICI in the clinical practice.