Professor Toi is passionate in his study of cancer, particularly breast cancer biology and treatment. He is keen on research that translates basic science into clinical study. He is involved in various innovative research projects on the development of new anticancer diagnostics and therapeutics including biomarkers, novel imaging and antibody treatment. He is engaged in clinical trials mainly associated with breast cancer treatment and research. He has a strong interest in the tumour microenvironment such as angiogenesis and stromal reactions.

Professor Toi belongs to various associations and is a member of several leading academic organizations. He serves as an editorial board member of multiple academic journals and has authored or co-authored over 300 articles.