PD-1 inhibition in malignant melanoma and lack of clinical response in chronic lymphocytic leukemia in the same patients: a case series
Chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the western world. Unfortunately these patients are often immunosuppressed and at increased risk of infection and secondary malignancy. Previous meta-analysis has found that patients with CLL are at a four-fold increase of melanoma compared to the general population. Recent advancements in our understanding of the programmed death (PD) receptor pathway have led to the advent of immunotherapies to target cancer cells. The use of PD-1 inhibitors is now considered first line treatment for BRAF wild-type metastatic melanoma. Interestingly, early pre-clinical data suggest that inhibition of this pathway may also be used in the treatment of CLL, however clinical trials now published were not successful. In this case series we highlight two cases where patients with CLL and concurrent malignant melanoma undergo treatment with PD-1 inhibitors, and were found to have reductions in their WBC counts but these were not sustained. These cases further illustrate that treatment of CLL with PD-1 inhibitors are ineffective treatment alone.