Relative to nivolumab monotherapy, an increase in progression-free survival (PFS) and overall survival (OS) for the combination of nivolumab with ipilimumab is established only in patients with low tumour PD-L1 expression.

...patients with previously untreated advanced melanoma to receive nivolumab at a dose of 1 mg per kilogram of body weight plus ipilimumab at a dose of 3 mg per kilogram every 3 weeks for four doses…better survival outcomes may be obtained with combination therapy than with monotherapy in patients with a lower tumor PD-L1 expression level (Figure 2)...123 patients with PD-L1 expression level of <1% had shown 3-yr progression-free survival rate and 3-yr overall survival rate of 35 and 54% respectively