Professor Baum is a leading British surgical oncologist who specialises in breast cancer treatment. He is also notable for his contributions to the evaluation and support of patient quality of life. He has been Professor of Surgery at King's College London, the Royal Marsden Hospital and UCL. He is a notable critic of alternative medicine.
In 2007, Baum received the St Gallen lifetime achievement award for the treatment of breast cancer.
Baum's team were the first to demonstrate the effectiveness of adjuvant tamoxifen for early breast cancer, which has contributed to the 30 per cent reduction in breast cancer mortality and its efficacy in the prevention of breast cancer in susceptible women. Since then, while at UCL, he was responsible for the largest-ever international cancer trial (ATAC - Arimidex, Tamoxifen, Alone or in Combination), which in record time showed anastrozole to be better than tamoxifen.
Baum was active in the successful campaign to retain the Royal Marsden's site at Fulham in central London.