Decrease in tumor content assessed in biopsies is associated with improved treatment outcome response to pembrolizumab in patients with rare tumors =================================================================================================================================================== * Coya Tapia * Phyu P. Aung * Sinchita Roy-Chowdhuri * Mingxuan Xu * Fengying Ouyang * Anas Alshawa * Joud Hajjar * Gopal Singh * Vincent Yang * Lilibeth Castillo * Hung Le * Ravi Murthy * Bettzy Stephen * Kenneth R Hess * Ignacio Wistuba * Aung Naing