This is a multi-center clinical study enrolling up to 86 participants. The primary objectives are to determine the objective response rate (ORR) established by the confirmed best overall response (BOR) following intratumoral administration of DaRT - Diffusing Alpha-Emitters Radiation Therapy, as well as to assess the Duration of Response (DOR) 6 months from initial response. Secondary objectives are to assess the safety of DaRT, and to assess the progression free survival (PFS), overall survival (OS), Overall Duration of Response (O-DOR), local control and quality of life (QOL) for patients treated with DaRT.