nivolumab based treatment
nivolumab alone
mHNSCC - 2nd line (L2)
mHNSCC - L2 - all population 4   
mHNSCC - L2 - PDL1 negative 2
mHNSCC - L2 - PDL1 positive 1
Comparator:  vs Standard of Care (SoC); 
Risk of bias:  low;   some concerns;   high;  NA;