Dr Shaffer is a cancer specialist who uses radiotherapy and chemotherapy to treat brain tumours, skin tumours, prostate cancer, and bladder cancer. His brain tumour team recently won an award for excellent clinical performance. He leads the Surrey technical radiotherapy development group, the network brain tumour group, and the intracranial stereotactic service. He is the principal investigator on several studies in brain tumours and prostate cancer.

Dr Shaffer has an interest in treating benign disease with radiotherapy, including early Dupuytren's disease, Ledderhose, and plantar fasciitis, and recently co-authored a national report on this subject through the Royal College of Radiologists.