Dr Sethi graduated with MBBS from the University of Singapore in 1971. After as a radiation oncologist, in the United Kingdom, he returned to Singapore to work in the Department of Radiation Oncology of the Singapore General Hospital and he has remained in service till today. Over the years, as a senior consultant radiation oncologist, he has held the following positions in the National Cancer Centre, Singapore (NCCS); Head of the department of Radiation Oncology, Chairman of the Medical Board, chair of its Research Ethics Board and is now NCCS senior advisor. He has a particular interest in breast cancer and malignant sarcoma.