Professor Berthold specialised in paediatric oncology and haematology, and palliative medicine, with a main scientific interest in clinical and translational research in neuroblastoma. He was Chairman of the German Neuroblastoma Group from 1985 to 2014, and in 2006–2008 President of the International Advances in Neuroblastoma Research Association and Chairman of the Advances in Neuroblastoma Research Congress, held in Cologne, 2014.

Following retirement in 2014 Professor Berthold holds a research position at the University of Cologne and is principal investigator of the metronomic I/II trial in neuroblastoma patients