I gave this talk via Skype for the Sociedad Española de Oncología Radioterápica (SEOR) XVIII Annual Congress today, 4 June 2015. The purpose was to explain hashtags, how they can organize content and help create community around health topics. After explaining how disease-specific tags may work, I discussed how radiation oncology can organize itself through online conversation. Radiation oncology is behind medical oncology but offers great value in cancer care. We should share it.