More on Merkel-Cell Carcinoma

To the Editor: Shiver et al. (Oct. 15 issue) 1 describe the efficacy of idelalisib in a patient with metastasis of Merkel-cell carcinoma to the liver. Activation of phosphoinositide 3-kinase (PI3K) signaling has long been identified in Merkel-cell carcinoma, 2 and this therapeutic intervention involving this pathway has great promise in the treatment of stage IV Merkel-cell carcinoma. However, the interpretation of this case requires some consideration. The authors do not mention radiation therapy as a possible confounder in the spectacular response. Indeed, the patient received hypofractionated radiation to the liver shortly before treatment with idelalisib was initiated. Given the high response . . .