Professor Thomas studied at Trinity College Cambridge and the London Hospital Medical College graduating in 1982. He trained at The London, Royal Free, St Mark's and St Mary's Hospitals. He was a Clinical Research Fellow at the Imperial Cancer Research Fund and wrote his PhD thesis on 'Molecular analysis of the Adenomatous Polyposis Coli gene region'. In 1994 he was appointed consultant physician and gastroenterologist at St Mary's and senior lecturer in the Imperial Cancer Research Fund Colorectal Cancer Unit at St Mark's. In 2007 he was appointed chair of gastrointestinal genetics at Imperial.
He heads the family cancer group at St Mark's. The aims of the group are to define the inherited predispositions to colorectal cancer and refine the management of familial risk.
His principal research interests are in the fields of:
Assessment of familial risk of colorectal cancer
Modification of familial risk by genetic testing
Colonoscopic surveillance for familial risk of colorectal cancer
Molecular genetic studies in familial colorectal cancer
Chemoprevention studies in familial colorectal cancer
He has long-standing collaborative research projects with Professor Peter Sasieni (Academic Director of Kings Clinical Trials Unit, King College London), Professor Ian Tomlinson FRS (Director of Edinburgh Cancer Research Centre) and Professor Sir John Burn (University of Newcastle).
He has been Head of HM Medical Household and Physician to the Queen since 2014. He was appointed KCVO in the 2021 New Year Honours.
et al., 2023, Mortality by age, gene and gender in carriers of pathogenic mismatch repair gene variants receiving surveillance for early cancer diagnosis and treatment: a report from the prospective Lynch syndrome database, Eclinicalmedicine, Vol:58, ISSN:2589-5370, Pages:1-12
et al., 2022, Colorectal cancer incidences in Lynch syndrome: a comparison of results from the prospective lynch syndrome database and the international mismatch repair consortium, Hereditary Cancer in Clinical Practice, Vol:20, ISSN:1731-2302, Pages:1-11
et al., 2022, Germline MBD4 deficiency causes a multi-tumor predisposition syndrome, American Journal of Human Genetics, Vol:109, ISSN:0002-9297, Pages:953-960
et al., 2020, Management strategies for the colonoscopic surveillance of people with Lynch syndrome during the COVID-19 pandemic, Gut, ISSN:0017-5749
et al., 2020, Cancer prevention with aspirin in hereditary colorectal cancer (Lynch syndrome), 10-year follow-up and registry-based 20-year data in the CAPP2 study: a double-blind, randomised, placebo-controlled trial, The Lancet, Vol:395, ISSN:0140-6736, Pages:1855-1863