New innovating cancer therapies are becoming available on the market. Because medical innovations put a serious financial burden on healthcare system, it is important to understand their diffusion. To analyze this process of diffusion, the molecule trastuzumab (Herceptin) provided by Roche Laboratories was chosen. Because Herceptin is commercialized since 1999 few data are available for this analysis. The objective of this study is to identify factors and brakes associated with the diffusion of the innovation Herceptin. By identifying these factors and brakes, one can notice that Herceptin is the perfect case to illustrate a successful diffusion. All factors mentioned in E. M. Rogers theory are verified with Herceptin: benefit, simplicity, triability, observability and compatibility. The tolerance is excellent and side effects minimized except for cardiac toxicity for patients previously treated with anthracyclines. The weakness concerning financing has been overcome since France changed the payment system to a prospective payment based on the hospital activity. The only problem left is that the fluorescence in situ hybridisation (FISH) test is still not reimbursed by the social security.