Desmoid disease occurs in one third of patients with familial adenomatous polyposis. Patients may be protected by changing surgical strategy. We designed a formula to predict desmoid risk and tested the value of adding genotype to the formula.
A desmoid risk factor was calculated by summing points awarded for gender (male = 1, female = 3), extracolonic manifestations (nil = 1, one = 2, >one = 3), and family history of desmoids (negative = 1, one relative = 2, more than one relative = 3). Performance of the score with and without genotype (5′ 1309 = 1, 1309–1900 = 2, 3′ 1900 = 3) was analyzed.
There were 839 patients (138 desmoids) without genotype and 154 (30 desmoids) with genotype. The mean desmoid risk factor score of patients without desmoids (no genotype) was 4.7 (±1.4 SD) and for patients with desmoid the desmoid risk factor was 6.0 (±1.7, P < 0.001). Corresponding data for patients with genotype was 6.1 ± 1.3 (no desmoids) and 8.4 ± 1.8 with desmoids (P < 0.001). Of patients without genotype, 648 patients were at low risk and 9.9% had desmoid disease, 178 patients were at medium risk and 34% had desmoids, and 10 patients were at high risk and all had desmoids. Of those with genotype information, 83 patients were at low risk and 5% had desmoids, 52 patients were at medium risk and 21% had desmoids, and 18 patients were at high risk and 83% had desmoids.
The desmoid risk factor identifies patients with various levels of risk for developing desmoid disease, and can be used to plan surgical strategies designed to minimize desmoid risk.