ORIGINAL ARTICLE Risk factors predicting intra-abdominal desmoids in familial adenomatous polyposis: a single centre experience A. Sinha • P. P. Tekkis • K. F. Neale • R. K. S. Phillips • S. K. Clark Received: 22 February 2010 / Accepted: 14 March 2010 / Published online: 30 March 2010 Ó Springer-Verlag 2010 Abstract Background Desmoids are myofibroblastic proliferations occurring in 15% of patients with familial adenomatous polyposis (FAP), 70% being intra-abdominal desmoids (IAD). Since the morbidity and mortality due to desmoids is almost entirely attributable to IAD, we aimed to identify specifically risk factors predicting IAD development in FAP. Methods We undertook a retrospective review of our institutional database. Multivariate analysis was performed, and hazard ratios (HR) calculated for variables including female gender, 3 0 APC mutation, surgical intervention for FAP (colectomy with ileo-rectal anastomosis or restorative proctocolectomy), age at surgery and family history (FH) of desmoids. Results Of the 558 patients analysed, 49 (9%) developed IAD; 22 (4%) diagnosed intra-operatively and 27 (5%) developing over a median post-operative period of 34 (7– 120) months. 75% of IAD had developed before age 40. A 3 0 APC mutation (HR 5.2, 95% CI 2.1–13.3, P = 0.001), positive FH (HR 2.5, 95% CI 1.4–4.6, P = 0.003) and female gender (HR 1.9, 95% CI 1.0–3.5, P = 0.04) were found to be predictive of IAD development. No significant difference in IAD risk was detected between the type of surgical intervention (P = 0.37) or age at surgery (P = 0.29). Conclusions Our analysis confirms 3 0 APC mutation to be the most significant risk factor for IAD development. The independent association between positive FH and IAD risk suggests the existence of modifier genes, independent of the APC genotype–phenotype correlation. Few of these risk factors can be meaningfully modified. Delaying prophy- lactic surgery may be appropriate in female patients with a 3 0 APC mutation and attenuated polyposis. Keywords Desmoid tumour Á Familial adenomatous polyposis Á Risk factors Introduction Familial adenomatous polyposis (FAP) is an autosomal dominant disease characterised by the development of hundreds to thousands of premalignant adenomatous pol- yps throughout the colorectum and duodenum [1]. Colo- rectal carcinoma develops if colectomy is not performed [2]. The usual choice of surgery lies between colectomy with an ileo-rectal anastomosis (IRA) or restorative proc- tocolectomy (RPC) [3, 4]. With improved endoscopic surveillance, the advent of genetic testing and prophylactic surgery, the extra-colonic manifestations of FAP are becoming more significant clinically [5, 6]. Duodenal polyposis and desmoid tumours (DT) are now the out- standing challenges in the management of patients with FAP. DT are rare myofibroblastic proliferations arising from musculo-aponeurotic tissue or the small bowel mesentery [7]. They can occur sporadically but are approximately a thousand times more common amongst patients with FAP. The lifetime incidence in this group is 10–25%, although subclinical disease is present in a greater percentage A. Sinha Á K. F. Neale Á R. K. S. Phillips Á S. K. Clark (&) Polyposis Registry, St. Mark’s Hospital and Imperial College, Northwick Park, Watford Road, Harrow, London HA1 3UJ, UK e-mail: sue.clark@nwlh.nhs.uk P. P. Tekkis Royal Marsden Hospital and Imperial College, London, UK 123 Tech Coloproctol (2010) 14:141–146 DOI 10.1007/s10151-010-0573-4