PDCD1 and obesity due to melanocortin 4 receptor deficiency: Obesity has been associated with increased efficacy of PD-1/PD-L1 blockade and attributed to T-cell dysfunction,29 and retrospective studies have shown that patients with obesity with breast cancer achieved the highest benefit.30 This benefit could be attributed to higher adipose tissue composition in the breast and augmented by metabolic syndrome conditions such as type 2 diabetes.