In 2013, the United States Food and Drug Administration approved radium-223 for the treatment of prostate cancer patients with bone metastases, based on the results of the ALSYMPCA trial. In doing so, radium-223 became the first approved anticancer agent that extended overall survival in cancer patients not by directly targeting the tumor, but by targeting its (skeletal) metastases. Radium-223 may effectively target bone metastases in other tumors as well, such as breast and lung cancer. Furthermore, considering its mechanism of action, it is likely that radium-223 will have antitumor activity in primary bone cancers such as osteosarcomas too. In this lecture, results of studies with radium-223 in tumors other than prostate cancer will be discussed.