The Central and East European Oncology Group (CEEOG) was established in 1983, initially as the South and East European Oncology Group (SEEOG). At the time, SEEOG comprised 15 institutions from Bulgaria, Czechoslovakia, Hungary, Poland, Romania and Yugoslavia. Over the first 16 years, the Group was chaired by Prof. Sandor Eckhardt from the National Cancer Institute in Budapest. SEEOG was then the only drug-oriented cancer research organization in the region. In the 1980s and 1990s, the Group conducted translational studies and phase II and III clinical trials in breast, ovarian, lung, and head and neck cancer patients.

In 1988, SEEOG changed its name to Central and East European Oncology Group (CEEOG), as the latter better reflected the geographical location of its member countries.

In 1999, CEEOG chairmanship was transferred to Prof. Jacek Jassem from the Medical University of Gdańsk, Poland, and Gdańsk became the home of the new Data Center.

Since its inception, CEEOG has experienced significant growth, expanding from its original 15 institutions to include around 35 academic and community hospitals. These institutions are located in Bosnia and Herzegovina, Bulgaria, Croatia, Czechia, Estonia, Hungary, Israel, Latvia, Lithuania, Poland, Romania, Serbia, Slovakia, Slovenia, and Switzerland.

CEEOG performs translational and investigator-initiated phase II clinical studies and participates in large phase III trials carried out within international consortia. The Group's primary focus is breast cancer. CEEOG is a Breast International Group (BIG) member and has participated in several pivotal BIG studies. Other global partners for cooperative activities in breast cancer include the EORTC (European Organisation for Research and Treatment of Cancer), IBCSG (International Breast Study Group), and the National Cancer Institute, Bethesda, USA (see  http://ceeog.eu/publications.html for the list of publications).

In 2005, CEEOG established its working party, the Polish Brain Metastasis Consortium (PBMC), chaired by Prof. Renata Duchnowska from the Military Institute of Medicine in Warsaw. PBMC has conducted several translational studies and now includes around 30 Polish and international institutions (see  http://www.pbmc.org.pl/en/publications/publications1.html for the list of publications).