Chondrosarcoma transformation in hereditary multiple exostoses: A systematic review and clinical and cost-effectiveness of a proposed screening model

BACKGROUND: The most serious complication of hereditary multiple exostoses(HME) is chondrosarcoma transformation. Numerous authors have suggested that screening might allow early chondrosarcoma detection. However, literature-quoted incidences of malignant transformation are highly variable. METHODS: A systematic review of malignant transformation by sex, exostosin-1 mutation(EXT1), age and site was conducted searching Medline, Embase and CINHAL. Three HME screening strategies were then developed and compared using cost per life-year gained and incremental cost-effectiveness ratio (ICER). RESULTS: Systematic review: 18 papers with 852 chondrosarcomas were identified. The incidence of chondrosarcoma transformation averaged 4%, 75.2% occurring between ages 20-40 and 56.2% at the pelvis and proximal femur. Screening model: In the general HME population, plain radiographs provided cost per life-year gain of £19,013 compared to £53,392 in MRIs. ICER in MRIs compared to X-rays was £80,218. However, for every generation of HME patients screened over 20 years, X-ray radiation induced 0.65 cancers. Psychological effects of false-positives were marginal. Screening only higher-risk groups (males or EXT1) reduced cost but benefited fewer patients. CONCLUSIONS: Our results suggest that annual MRI screening for all HME patients between age 20-40 may be of value. However, the extent of anatomical imaging is subject to debate; it is possible that focused imaging protocols which scan from cervical spine to proximal femur may improve cost-effectiveness.